Search a number
octagonal n.  and  tau n.

First numbers that belong to both sets:

1, 8, 40, 96, 225, 560, 936, 1408, 1680, 2640, 3816, 4720, 6816, 12160, 26320, 31008, 32240, 36080, 42960, 61920, 67200, 90480, 99008, 107920, 110208, 117216, 150080, 172320, 193040, 208560, 218160, 231296, 234640, 306560, 334000, 338016, 350208, 354320, 388080, 418880, 455520, 493696, 513360, 518336, 538480, 553840, 559008, 579920, 601216, 606600, 707616, 731120, 761040, 779280, 810160, 835296, 854400, 987280, 994176, 1015008, 1022000, 1043120, 1078800, 1189440, 1281840, 1313408, 1321360, 1345360, 1353408, 1377696, 1385840, 1485440, 1553760, 1659120, 1686000, 1731280, 1795680, 1870720, 1986160, 1995936, 2025408, 2035280, 2065040, 2075008, 2115120, 2237760, 2268960, 2332008, 2395920, 2449840, 2493408, 2526336, 2537360, 2762880, 2797536, 2844080, 2902800, 2938320, 2998000, 3046176, 3330640, 3381408, 3432560, 3497040, 3549056, 3654240, 3694080, 3760960, 3855600, 4020576, 4034480, 4132480, 4418960, 4433536, 4492080, 4536240, 4685000, 4836160, 4912640, 5020720, 5083008, 5098640, 5145680, 5161408, 5224560, 5464800, 5660880, 5793520, 5810208, 6131840, 6269856, 6339440, 6426960, 6479760, 6497408, 6568240, 6639456, 6982976, 7148720, 7278976, 7297680, 7524000, 7811760, 7908880, 7967440, 8045856, 8065520, 8524416, 8768880, 8851136, 8871760, 8954496, 9289280, 9437680, 9458976, 9608720, 9716400, 9868160, 10308240, 10419760, 10486960, 10509408, 10576896, 10599440, 11310208, 11333520, 11403600, 11615136, 11686080, 12164560, 12188736, 12261408, 12285680, 12358640, 12776160, 12850560, 13150320, 13276240, 13352080, 13377408, 13453536, 14070336, 14174480, 14305200, 14383920, 14489216, 14621376, 15048320, 15264096, 15372560, 15454160, 15920640, 16226176, 16478320, 16704080, 16817536, 17361696, 17477360, 17593408, 17622480, 17709840, 17855920, 17973216, 18061440, 18208960, 18238536, 18685056, 18775008, 18805040, 18895280, 19046160, 19655680, 19871280, 20119120, 20243616, 20650880, 21125840, 21157696, 21285360, 21541840, 21767520, 22026880, 22451616, 22583120, 22682000, 22715008, 22847280, 23346720, 24021040, 24055008, 24191120, 24704960, 24877440, 24981216, 25119920, 25293840, 25398480, 25433408, 25573360, 25713696, 26385536, 26528080, 27138176, 27755208, 27974640, 28121408, 28158160, 28268560, 28305408, 29196960, 29761200, 29950480, 30982960, 31137408, 31176080, 32072160, 32742640, 32861680, 32901408, 33020736, 33060560, 33862080, 33983136, 34347600, 34510208, 34836576, 35824896, 35949408, 35990960, 36115760, 36282496, 36827040, 36953280, 37164160, 37460400, 37672720, 37843008, 37970976, 38013680, 39002496.

Some larger examples :