%I #10 Dec 19 2016 02:08:29

%S 4,12,16,28,36,40,52,60,72,88,96,100,108,112,136,148,156,172,180,192,

%T 196,228,232,240,256,268,276,280,292,312,316,336,348,352,372,388,396,

%U 400,408,420,432,448,456,460,508,520,540,556,568,576,592,600,612,616

%N a(n) = 4*A005098(n) = A002144(n) - 1.

%C 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 1 2 3 4

%C 2 4 1 3

%C 3 1 4 2

%C 4 3 2 1

%C 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 1, A002314(n), A152676(n), A152680(n) are subfields of the Galois Field [A002144(n)].

%C Numbers n such that A172019(n) + 1 = primes - 1. - _Giovanni Teofilatto_, Feb 02 2010

%t aa = {}; Do[If[Mod[Prime[n], 4] == 1, AppendTo[aa, Prime[n] - 1]], {n, 1, 200}]; aa

%Y Cf. A002314, A152676, A152680.

%K nonn

%O 1,1

%A _Artur Jasinski_, Dec 10 2008