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 A165354 #18 Jan 09 2025 02:54:30
%S A165354 3,5,11,13,19,29,37,43,47,53,59,61,67,83,89,97,101,107,109,131,137,
%T A165354 139,149,157,163,167,173,179,181,193,197,199,211,223,227,229,239,241,
%U A165354 251,263,269,271,277,283,293,307,313,317,331,347,349,353,359,373,379,389
%N A165354 Primes p such that p+(p^2-1)/8 is an integer but not a prime number.
%C A165354 For p=2, p+(p^2-1)/8 is not integer; for all others, p=4k+-1, it is an integer.
%H A165354 Vincenzo Librandi, <a href="/A165354/b165354.txt">Table of n, a(n) for n = 1..1000</a>
%F A165354 A000040 \ {{2} U A165353}. - _R. J. Mathar_, Sep 21 2009
%t A165354 Select[Prime[Range[2, 500]], ! PrimeQ[(#^2 - 1) / 8 + #]&] (* _Vincenzo Librandi_, Sep 12 2013 *)
%o A165354 (Magma) [p: p in PrimesUpTo(500)| not IsPrime(Floor(p+(p^2-1)/8))]; // _Vincenzo Librandi_, Sep 12 2013
%Y A165354 Cf. A165352, A165353.
%K A165354 nonn,easy
%O A165354 1,1
%A A165354 _Vincenzo Librandi_, Sep 16 2009
%E A165354 Entries checked by _R. J. Mathar_, Sep 21 2009