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 A063780 Numbers n such that there exist sequences a_i, b_i in N (i=1,2,3,4) with 0 < a_1 < a_2 < a_3 < a_4 < n, 0 < b_1 < b_2 < b_3 < b_4 < n and a_i != b_j for all i,j = 1,2,3,4, satisfying (1) sum_{i=1..4} a_i = sum_{i=1..4} b_i = 2*n, (2) prod_{i=1..4} cos (a_i * Pi / (2*n)) = prod_{i=1..4} cos (b_i * Pi / (2*n)). 0
 20, 21, 24, 25, 30, 33, 35, 36, 40, 42, 45, 48, 50, 54, 55, 57, 60, 65, 66, 70, 75, 78, 80, 84, 85, 90, 95, 96, 99, 100, 102, 105, 106, 108, 109, 110, 114, 115, 118, 120, 125, 126, 128, 129, 130, 132, 133, 134, 135, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS CROSSREFS Sequence in context: A138602 A326678 A030605 * A125663 A241850 A138601 Adjacent sequences:  A063777 A063778 A063779 * A063781 A063782 A063783 KEYWORD nonn AUTHOR Eckard Specht (eckard.specht(AT)physik.uni-magdeburg.de) Aug 17 2001 STATUS approved

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Last modified October 20 10:00 EDT 2019. Contains 328257 sequences. (Running on oeis4.)