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 A179458 #20 Jun 28 2024 09:29:43 %S A179458 1,3,5,7,11,13,15,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83, %T A179458 85,89,91,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167, %U A179458 173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,307 %N A179458 Numbers k such that ((2^(2k) - 1) mod 2k) - (2^(2k-1) mod 2k) = 1. %C A179458 Apparently, the sequence contains 1, odd primes and the elements of A020136. - _R. J. Mathar_, Jan 09 2011 %H A179458 Robert Israel, <a href="/A179458/b179458.txt">Table of n, a(n) for n = 1..10000</a> %p A179458 select(n -> (2 &^ (2*n)-1 mod 2*n)-(2 &^(2*n-1) mod 2*n) = 1, [$1..1000]); # _Robert Israel_, Oct 25 2017 %o A179458 (PARI) isok(n) = (((2^(2*n)-1) % (2*n)) - (2^(2*n-1) % (2*n)) == 1) \\ _Michel Marcus_, Jul 25 2013 %Y A179458 Cf. A001567. %K A179458 nonn %O A179458 1,2 %A A179458 _Juri-Stepan Gerasimov_, Jan 07 2011