A276688 a(n) = Im([n]_{1+i}!), where [n]_q! is the q-factorial, i = sqrt(-1).

0, 0, 1, 8, 5, -220, 1895, -9140, -302175, -2778300, -95631825, -10071428100, -236788407375, 57706241794500, -7412904844112625, 525300693117661500, 348922898045520800625, 55166584329677385922500, 28368558145043150339199375, 46873210124734003815040957500

Offset: 0

Author

Vladimir Reshetnikov, Sep 13 2016

Keywords

• sign

Links

• Eric Weisstein's World of Mathematics, q-Factorial.

Crossrefs

Cf. A275706 (real part), A005329.

Programs

Maple

a:= n-> Im(mul(((1+I)^j-1)/((1+I)-1), j=1..n)):
seq(a(n), n=0..20);  # Alois P. Heinz, Sep 14 2016

Mathematica

Im@Table[QFactorial[n, 1 + I], {n, 0, 20}]