This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A129497 #12 Jul 24 2021 05:39:06 %S A129497 14,21,25,42,50,56,58,62,70,74,82,84,86,94,98,105,106,112,118,122,132, %T A129497 133,134,142,146,147,150,152,158,166,168,178,182,194,196,202,206,210, %U A129497 214,218,226,231,254,262,266,274,278,294,298,301,302,314,325,326,334 %N A129497 Composite numbers k such that 7^k (mod k) is a power of 7 greater than 1. %H A129497 Amiram Eldar, <a href="/A129497/b129497.txt">Table of n, a(n) for n = 1..10000</a> %e A129497 58 is a member of the sequence since 7^58 (mod 58) == 49. %t A129497 Select[Range@ 335, (p = PowerMod[7, #, #]) > 1 && IntegerQ@ Log[7, p] && CompositeQ[#] &] (* corrected by _Amiram Eldar_, Jul 24 2021 *) %Y A129497 Cf. A036236, A129492, A129493, A129494, A129495, A129496. %K A129497 easy,nonn %O A129497 1,1 %A A129497 _Robert G. Wilson v_, Apr 17 2007 %E A129497 Corrected and edited by _R. J. Mathar_, May 16 2008