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 A063781 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} sin (a_i * Pi / (2*n)) = prod_{i=1..4} sin (b_i * Pi / (2*n)). 1

%I

%S 15,18,20,24,25,30,33,35,36,40,42,45,48,50,54,55,57,60,63,65,66,70,72,

%T 75,78,80,84,85,90,95,96,99,100,102,105,106,108,109,110,114,115,118,

%U 120,125,126,128,129,130,132,133,134,135,137,138,139,140,141,142,143

%N 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} sin (a_i * Pi / (2*n)) = prod_{i=1..4} sin (b_i * Pi / (2*n)).

%K nonn

%O 1,1

%A Eckard Specht (eckard.specht(AT)physik.uni-magdeburg.de) Aug 17 2001

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Last modified April 3 01:31 EDT 2020. Contains 333195 sequences. (Running on oeis4.)