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 A069254 #17 Jun 14 2022 02:28:06 %S A069254 1,3,7,9,11,13,17,19,21,23,27,29,31,33,37,43,47,49,51,53,57,59,61,63, %T A069254 67,69,71,73,77,79,81,83,87,89,91,93,97,99,101,103,107,109,111,113, %U A069254 119,121,127,129,131,133,137,139,141,143,147,149,151,153,157,159,161,163 %N A069254 k/10 when gcd(k, 2^k+1) = 5. %C A069254 The number of terms not exceeding 10^m, for m = 1, 2, ..., are 4, 38, 371, 3726, 37259, 372542, 3725411, 37254006, 372539990, ... . Apparently, the asymptotic density of this sequence exists and equals 0.3725... . - _Amiram Eldar_, Jun 14 2022 %H A069254 Amiram Eldar, <a href="/A069254/b069254.txt">Table of n, a(n) for n = 1..10000</a> %t A069254 Select[Range[170], GCD[10*#, PowerMod[2, 10*#, 10*#] + 1] == 5 &] (* _Amiram Eldar_, Jun 14 2022*) %o A069254 (PARI) lista(nn) = select(x->(gcd(x, 2^x+1) == 5), [1..nn])/10 \\ _Michel Marcus_, Oct 27 2019 %Y A069254 Cf. A069226. %K A069254 easy,nonn %O A069254 1,2 %A A069254 _Benoit Cloitre_, Apr 13 2002