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 A301812 #13 Mar 28 2018 12:51:30
%S A301812 3,24,120,288,528,840,1680,2208,2808,3480,5040,6888,7920,10200,11448,
%T A301812 12768,17160,18768,22200,27888,29928,32040,36480,38808,51528,54288,
%U A301812 57120,63000,66048,69168,72360,78960,85848,96720,100488,120408,124608,128880,146688
%N A301812 Numbers of the form p^2 - 1 where p is a prime of the form 3*k-1 (A003627).
%F A301812 a(n) = A003627(n)^2 - 1. - _Altug Alkan_, Mar 28 2018
%p A301812 A301812List := proc(len) local p, n, L; L := 3; p := 5;
%p A301812 for n from 2 to len do if isprime(p) then L := L,(p^2 - 1) fi;
%p A301812 p := p + 6; od: L end:
%p A301812 A301812List(65);
%t A301812 Flatten[Table[n^2 - 1, {n, {2, Select[Range[5, 385, 6], PrimeQ]}}]]
%Y A301812 Cf. A003627, A084920.
%K A301812 nonn,easy
%O A301812 1,1
%A A301812 _Peter Luschny_, Mar 27 2018