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 A316906 #13 Apr 03 2021 08:43:08 %S A316906 7957,23377,30889,35333,42799,49981,60787,91001,129889,150851,162193, %T A316906 164737,241001,249841,253241,256999,280601,318361,387731,452051, %U A316906 481573,556169,580337,617093,665333,722201,838861,877099,1016801,1251949,1252697,1325843,1507963 %N A316906 Numbers k such that 2^(k-1) == 1 (mod k) and lpf(k)-1 does not divide k-1. %C A316906 Are there infinitely many such pseudoprimes? %H A316906 Amiram Eldar, <a href="/A316906/b316906.txt">Table of n, a(n) for n = 1..10000</a> %e A316906 7957 = 73*109 is pseudoprime and 72 does not divide 7956. %e A316906 30889 = 17*23*79 is pseudoprime and 16 does not divide 30888. %t A316906 Select[Range[760000] 2 + 1, PowerMod[2, #-1, #] == 1 && Mod[#-1, FactorInteger[#][[1, 1]] - 1] > 0 &] (* _Giovanni Resta_, Jul 16 2018 *) %Y A316906 Subsequence of A001567. %Y A316906 Cf. A020639 (lpf(n)). %K A316906 nonn %O A316906 1,1 %A A316906 _Thomas Ordowski_, Jul 16 2018 %E A316906 a(8)-a(33) from _Giovanni Resta_, Jul 16 2018