2026-10-28T14:57:39Z https://nostr.now John D. Cook https://nostr.now/npub196uf0rky2aes0v9ejr994z7h85reg5f9fnxu0eumtm0fue2gjeasn8kntt https://media.mathstodon.xyz/accounts/avatars/109/382/868/019/399/709/original/dec8ccd84b88f1da.jpg https://media.mathstodon.xyz/accounts/avatars/109/382/868/019/399/709/original/dec8ccd84b88f1da.jpg https://nostr.now/nevent1qqsdfvd7ksj5kny3jld9lg2asrpfvnf493tnvsahwwfl925rgluvx2szyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8k27j9y3 The product of four consecutive Fibonacci numbers equals the product of two consecutive integers. For example,<br/><br/>3 × 5 × 8 × 13 = 39 × 40.<br/><br/><a href="https://www.johndcook.com/blog/2026/09/16/fibonacci-product/">https://www.johndcook.com/blog/2026/09/16/fibonacci-product/</a> 2026-09-16T12:11:31Z https://nostr.now/nevent1qqsvxvj340j04w7y8smn5wkyhjql0z907hg2lsvv64md6lwq7ml5hrgzyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8kv86z5a Fitting a regular expression to a list of words<br/><br/><a href="https://www.johndcook.com/blog/2026/07/19/fitting-a-regex/">https://www.johndcook.com/blog/2026/07/19/fitting-a-regex/</a> 2026-07-19T19:32:39Z https://nostr.now/nevent1qqsvvkw59lhru6zevaw4nm66cmnfnkq6w5mlakt08xnt3q44t2va7wszyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8k33zl89 <img src="https://media.mathstodon.xyz/media_attachments/files/116/720/287/848/353/774/original/b20a348119cf1881.png"> <br/> 2026-06-09T13:04:17Z https://nostr.now/nevent1qqsp6vt65yrqfzw7rt3jwnjxxlksjualf9ucjv829qatppkd9yplfcgzyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8kuhvv4q <a href="https://www.johndcook.com/blog/2026/02/24/a-curious-trig-identity/">https://www.johndcook.com/blog/2026/02/24/a-curious-trig-identity/</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/116/128/226/380/161/184/original/261048f23152e6f8.png"> <br/> 2026-02-24T23:35:15Z https://nostr.now/nevent1qqsrdysldhj2krpr5gz45l39wyhq58yypjg9zclgnx3q6q4nyudg86qzyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8k4uajgn A knight&#39;s tour with the fewest possible obtuse angles. Reproduced from Donald Knuth&#39;s latest Christmas Lecture.<br/><br/><a href="https://www.johndcook.com/blog/2025/12/31/knights-tour-minimum-obtuse/">https://www.johndcook.com/blog/2025/12/31/knights-tour-minimum-obtuse/</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/814/507/542/326/351/original/23258222c8189ce0.png"> <br/> 2025-12-31T13:52:56Z https://nostr.now/nevent1qqsxd5vpvugvlnd4auheyu4k33t87mz2t3nll6us09u6dcjvkqpl52qzyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8kg24akk AI Automation and Validation: Who watches the watchmen?<br/><br/><a href="https://www.johndcook.com/blog/2025/12/24/automation-and-validation/">https://www.johndcook.com/blog/2025/12/24/automation-and-validation/</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/774/962/195/897/472/original/a4973a135436a8b4.jpg"> <br/> 2025-12-24T14:16:03Z https://nostr.now/nevent1qqsfm7x2nphshd07w2rrx9923xup2rxat0s9sv4mx3mz8tcgvg7ywtgzyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8k7unkdj Monero subaddresses <br/><a href="https://www.johndcook.com/blog/2025/11/28/monero-subaddresses/">https://www.johndcook.com/blog/2025/11/28/monero-subaddresses/</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/629/479/357/786/879/original/37f81c73d0e79e30.jpeg"> <br/> 2025-11-28T21:37:26Z https://nostr.now/nevent1qqsd3y6rkgjf36ffukza5s0xxat2h24xllldw9dqj4srqznu3uxs55qzyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8kc8zkad The graph below appears to show that the correlation between two stocks peaks about every 50 days. But this is purely an analysis artifact. The two series are in fact independent random walks. Shows how analysis can be misleading.<br/><br/><a href="https://www.johndcook.com/blog/2025/11/09/rolling-correlation/">https://www.johndcook.com/blog/2025/11/09/rolling-correlation/</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/521/287/707/766/819/original/b7abbf7ccaba7996.png"> <br/> 2025-11-09T19:03:03Z https://nostr.now/nevent1qqsxrshfa4k97z6azr9d8gk9yzg34c899cly78v9y6zr2z3r8px4p9szyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8k74m2qk In reply to <a href='/nevent1qqsgmq54knfycvsgd8aedujuqla8jfthz7mlvp2vkp3dklxxt6wy8ygphs0pc'>nevent1q…s0pc</a><br/>_________________________<br/><br/>Thanks! <br/><br/>Of course we can always repurpose symbols as math symbols. Seems like the new symbol could be useful in infinity category theory. Maybe the upside down symbol could be used for its dual. :) 2025-09-10T14:03:49Z https://nostr.now/nevent1qqsys27a2q3rhlvesezm4zjc860y4qpadynk78r63x9ng78k3vc6edqzyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8kwmx258 An uncrossed knight&#39;s tour<br/>From a paper by Donald Knuth<br/><br/><a href="https://www.johndcook.com/blog/2025/08/29/an-uncrossed-knights-tour/">https://www.johndcook.com/blog/2025/08/29/an-uncrossed-knights-tour/</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/115/112/034/551/312/313/original/87b9155f63ce66a4.png"> <br/> 2025-08-29T12:24:19Z https://nostr.now/nevent1qqsy4nmcnlscm6n40j7cu56x3phzc9nx86wq7gjy3tf6cqqzx8unjwszyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8k5gtddc Connection between π and Fibonacci numbers<br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/857/574/776/152/426/original/63a15483e9ea6bae.png"> <br/> 2025-07-15T13:52:15Z https://nostr.now/nevent1qqs8ccj207rqlfyxrmuvcp2yz6sl9crr4jrv3npttpvfhdk0f7tjrcgzyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8kfxsrw7 What exactly is Bitcoin&#39;s proof-of-work task?<br/><br/>Popular descriptions aren&#39;t quite right.<br/><br/><a href="https://www.johndcook.com/blog/2025/06/20/bitcoin-proof-of-work/">https://www.johndcook.com/blog/2025/06/20/bitcoin-proof-of-work/</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/715/970/469/922/169/original/ef15e5777cda236f.jpg"> <br/> 2025-06-20T13:40:15Z https://nostr.now/nevent1qqsqmrnpe6l9wdhst56dz6zjsj0tcs0m3lmxry56xj2e6lr6dj40ztszyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8kd6kw7n Special solutions to the 8 queens problem<br/><br/><a href="https://www.johndcook.com/blog/2025/05/11/eight-queens-symmetry/">https://www.johndcook.com/blog/2025/05/11/eight-queens-symmetry/</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/490/282/886/951/425/original/ea2761d2fdf2b5c6.png"> <br/> 2025-05-11T17:04:39Z https://nostr.now/nevent1qqsve3lsnzstvpy9pyhu3c2hz2axnl2x2r0zcg0f63gugpfayrjldpgzyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8k5l73h3 Multiplication tables and Latin squares<br/><br/><a href="https://www.johndcook.com/blog/2025/02/19/cayley-table-latin-square/">https://www.johndcook.com/blog/2025/02/19/cayley-table-latin-square/</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/114/031/207/628/408/674/original/7c1af80312cf8787.png"> <br/> 2025-02-19T15:15:56Z https://nostr.now/nevent1qqs87jmw5n369nt0ctk4m09l2hvgku452tltsruqughh7wr2uwyturczyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8kfncrkc Efficiently transferring to a much higher orbit<br/><br/><a href="https://www.johndcook.com/blog/2024/12/03/bi-elliptic-transfer/">https://www.johndcook.com/blog/2024/12/03/bi-elliptic-transfer/</a><br/> <img src="https://media.mathstodon.xyz/media_attachments/files/113/589/551/408/471/615/original/4c4de10a9be9e063.png"> <br/> 2024-12-03T15:16:48Z https://nostr.now/nevent1qqsgufucjt59ttlrg8w4fnxeku5d9ms8ar5ly3qqqrgarlauugjergqzyqht39uwc3thxpashxgv5k5t6u7s09z3y4xvm3l8nd0da8n9fzt8khnecr7 Arithmetic, Geometry, Harmony, and Gold<br/><br/><a href="https://www.johndcook.com/blog/2024/09/17/four-means/">https://www.johndcook.com/blog/2024/09/17/four-means/</a> 2024-09-17T14:07:54Z