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 A152680 #10 Dec 19 2016 02:08:29
%S A152680 4,12,16,28,36,40,52,60,72,88,96,100,108,112,136,148,156,172,180,192,
%T A152680 196,228,232,240,256,268,276,280,292,312,316,336,348,352,372,388,396,
%U A152680 400,408,420,432,448,456,460,508,520,540,556,568,576,592,600,612,616
%N A152680 a(n) = 4*A005098(n) = A002144(n) - 1.
%C A152680 If we take the 4 numbers 1, A002314(n), A152676(n), A152680(n) then the multiplication table modulo A002144(n) is isomorphic with the Latin square
%C A152680 1 2 3 4
%C A152680 2 4 1 3
%C A152680 3 1 4 2
%C A152680 4 3 2 1
%C A152680 and isomorphic with the multiplication table of {1,I,-I,-1} where I is sqrt(-1), A152680(n) is isomorphic with -1, A002314(n) with I or -I and A152676(n) vice versa -I or I.
%C A152680 1, A002314(n), A152676(n), A152680(n) are subfields of the Galois Field [A002144(n)].
%C A152680 Numbers n such that A172019(n) + 1 = primes - 1. - _Giovanni Teofilatto_, Feb 02 2010
%t A152680 aa = {}; Do[If[Mod[Prime[n], 4] == 1, AppendTo[aa, Prime[n] - 1]], {n, 1, 200}]; aa
%Y A152680 Cf. A002314, A152676, A152680.
%K A152680 nonn
%O A152680 1,1
%A A152680 _Artur Jasinski_, Dec 10 2008