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 A241264 #18 Sep 08 2022 08:46:07 %S A241264 4,13,20,24,26,30,31,32,35,36,37,38,40,41,43,47,49,51,54,55,60,62,63, %T A241264 64,67,70,71,72,73,75,76,78,79,81,82,84,85,88,89,92,94,97,98,100,102, %U A241264 105,108,109,111,112,113,114,115,117,118,119,120,122,123,124,125 %N A241264 Numbers k such that 2*k^2 + 2*k - 41 is not a prime. %H A241264 Vincenzo Librandi, <a href="/A241264/b241264.txt">Table of n, a(n) for n = 1..5000</a> %e A241264 13 is in this sequence because 2*13^2 + 2*13 - 41 = 323 = 17*19. %t A241264 Select[Range[4, 200], ! PrimeQ[2 #^2 + 2 # - 41] &] %o A241264 (Magma) [n: n in [1..150] | not IsPrime(2*n^2+2*n-41)]; %Y A241264 Complement of A155771. %K A241264 nonn,easy %O A241264 1,1 %A A241264 _Vincenzo Librandi_, Apr 20 2014