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 A172095 #13 Aug 30 2025 14:37:39 %S A172095 3,5,7,9,11,13,17,19,27,37,53,107,163,243,2187,2917,4373,8747,1594323, %T A172095 86093443 %N A172095 Integers k such that k-1,k,k+1 have few distinct primes: k=p^r, p odd prime, and (k^2-1)/8 divisible by at most two distinct prime factors. %C A172095 Note the terms 3^1=3, 3^2=9, 3^3=27, 3^5=243, 3^7=2187, and 3^13=1594323. The other listed terms are prime. %C A172095 Next term > 2^2000. - _Max Alekseyev_, Feb 16 2011 %Y A172095 Cf. A075081, A062547, A111974, A005105 %K A172095 nonn,hard,more,changed %O A172095 1,1 %A A172095 Dino Lorenzini (lorenzin(AT)uga.edu), Jan 25 2010 %E A172095 Edited and missing terms 3, 5, 9, 17 added by _Max Alekseyev_, Feb 16 2011