A302662 Imaginary part of Product_{k=1..n} (k+(n-k+1)i), with i=sqrt(-1).

0, 1, 5, 20, 0, -1560, -26825, -272000, 0, 84086080, 2484885325, 40560998400, 0, -28152429760000, -1180588763732625, -26582971351040000, 0, 32774236110420480000, 1780605230870046303125, 51128938217766256640000, 0, -98456230888859903488000000, -6569779608356896665959265625

Offset

0,3

Comments

a(n) = 0 when n is a multiple of 4 (A008586). - Michel Marcus, Apr 11 2018

Links

Seiichi Manyama, Table of n, a(n) for n = 0..398

Maple

seq(Im(mul(k+(n-k+1)*I, k=1..n)), n=0..30); # Muniru A Asiru, Apr 11 2018

Prog

(PARI) {a(n) = imag(prod(k=1, n, k+(n-k+1)*I))}

Crossrefs

Cf. A008586, A301616.

Real part: A302661.

Sequence in context: A357517 A122152 A104314 * A261545 A093482 A283522

Adjacent sequences: A302659 A302660 A302661 * A302663 A302664 A302665

Keyword

sign

Author

Seiichi Manyama, Apr 11 2018

Status

approved