a(n) is the number of pairs of integer quadruples (b_1, b_2, b_3, b_4) and (c_1, c_2, c_3, c_4) satisfying 1 <= b_1 < b_2 < b_3 < b_4 < n, 1 <= c_1 < c_2 < c_3 < c_4 < n, b_i != c_j for all i,j = 1,2,3,4 and Product_{i=1..4} cos(2*Pi*b_i/n) = Product_{i=1..4} cos(2*Pi*c_i/n).
A063780
a(n) is the number of pairs of integer quadruples (b_1, b_2, b_3, b_4) and (c_1, c_2, c_3, c_4) satisfying 1 <= b_1 < b_2 < b_3 < b_4 < n, 1 <= c_1 < c_2 < c_3 < c_4 < n, b_i != c_j for all i,j = 1,2,3,4 and Product_{i=1..4} cos(2*Pi*b_i/n) = Product_{i=1..4} cos(2*Pi*c_i/n).
Terms
- a(0) =0a(1) =1a(2) =3a(3) =4a(4) =9a(5) =9a(6) =18a(7) =17a(8) =93a(9) =29a(10) =84a(11) =45a(12) =433a(13) =66a(14) =253a(15) =93a(16) =1274a(17) =126a(18) =534a(19) =166a(20) =2940a(21) =214a(22) =1120a(23) =270a(24) =5866a(25) =335a(26) =1601a(27) =410a(28) =11359a(29) =495
External references
- oeis: A063780