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 A152680 a(n) = 4*A005098(n) = A002144(n) - 1. 7
 4, 12, 16, 28, 36, 40, 52, 60, 72, 88, 96, 100, 108, 112, 136, 148, 156, 172, 180, 192, 196, 228, 232, 240, 256, 268, 276, 280, 292, 312, 316, 336, 348, 352, 372, 388, 396, 400, 408, 420, 432, 448, 456, 460, 508, 520, 540, 556, 568, 576, 592, 600, 612, 616 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 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 1 2 3 4 2 4 1 3 3 1 4 2 4 3 2 1 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. 1, A002314(n), A152676(n), A152680(n) are subfields of the Galois Field [A002144(n)]. Numbers n such that A172019(n) + 1 = primes - 1. - Giovanni Teofilatto, Feb 02 2010 LINKS MATHEMATICA aa = {}; Do[If[Mod[Prime[n], 4] == 1, AppendTo[aa, Prime[n] - 1]], {n, 1, 200}]; aa CROSSREFS Cf. A002314, A152676, A152680. Sequence in context: A320922 A028594 A239050 * A270248 A228274 A273501 Adjacent sequences:  A152677 A152678 A152679 * A152681 A152682 A152683 KEYWORD nonn AUTHOR Artur Jasinski, Dec 10 2008 STATUS approved

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Last modified September 30 19:57 EDT 2020. Contains 337440 sequences. (Running on oeis4.)