A275706 a(n) = Re([n]_{1+i}!), where [n]_q! is the q-factorial, i = sqrt(-1).

1, 1, 2, 1, -40, 135, -860, 20145, -137100, -6726225, -212460900, -3642898575, 654642826500, -26505894416625, 3335048243533500, -1368325090374591375, 133951676745003682500, 123266968248328746879375, 63057521158814641016317500, 17732380504905960076345280625

Offset: 0

Author

Vladimir Reshetnikov, Sep 13 2016

Keywords

• sign

Links

• Robert Israel, Table of n, a(n) for n = 0..114
• Eric Weisstein's World of Mathematics, q-Factorial.

Crossrefs

Cf. A276688 (imaginary part), A005329.

Programs

Maple

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

Mathematica

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