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 A176176 #20 Feb 11 2021 01:20:33 %S A176176 1,2,3,4,5,7,8,11,13,16,17,19,23,28,29,31,32,37,41,43,47,53,59,61,64, %T A176176 67,71,73,79,83,89,97,101,103,107,109,112,113,127,128,131,137,139,149, %U A176176 151,157,163,167 %N A176176 Numbers k such that 2^(k-1) == 4^(k-1) (mod k). %C A176176 Numbers k such that A062173(k) = A062175(k). %C A176176 Question: is the sequence (Powers of 2) UNION (odd primes), the union of A000079 and A005408? %C A176176 The answer to the question is no: 2^(28-1) mod 28 = 4^(28-1) mod 28 = 8. Also, any base-2 Fermat pseudoprime (A001567) is a term of this sequence. - _D. S. McNeil_, Dec 07 2010 %H A176176 Harvey P. Dale, <a href="/A176176/b176176.txt">Table of n, a(n) for n = 1..10000</a> %t A176176 Select[Range[200],PowerMod[2,#-1,#]==PowerMod[4,#-1,#]&] (* _Harvey P. Dale_, Nov 10 2011 *) %Y A176176 Cf. A000079, A005408, A062173. %K A176176 nonn %O A176176 1,2 %A A176176 _Juri-Stepan Gerasimov_, Dec 07 2010 %E A176176 Extended by _D. S. McNeil_, Dec 07 2010