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A105751 Imaginary part of Product_{k=0..n} 1+k*I, I=sqrt(-1). 2
0, 1, 3, 0, -40, -90, 1050, 6160, -46800, -549900, 3103100, 67610400, -271627200, -11186357000, 26495469000, 2416003824000, -1394099824000, -662595375078000, -936096296850000, 225382826562400000, 819329864480400000, -93217812901913700000, -570263312237604700000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Seiichi Manyama, Table of n, a(n) for n = 0..450

FORMULA

a(n) = ((2*n-1)*a(n-1)-(n^2-2*n+2)*n*a(n-2))/(n-1) for n > 1, a(n) = n for n < 2. - Alois P. Heinz, Apr 11 2018

MAPLE

a:= proc(n) option remember; `if`(n<2, n,

      ((2*n-1)*a(n-1)-(n^2-2*n+2)*n*a(n-2))/(n-1))

    end:

seq(a(n), n=0..25);  # Alois P. Heinz, Apr 11 2018

PROG

(PARI) a(n) = imag(prod(k=0, n, 1+k*I)); \\ Michel Marcus, Apr 11 2018

CROSSREFS

Cf. A003703, A009454, A105750, A231531.

Sequence in context: A157310 A172396 A164806 * A177698 A009786 A012738

Adjacent sequences:  A105748 A105749 A105750 * A105752 A105753 A105754

KEYWORD

easy,sign

AUTHOR

Paul Barry, Apr 18 2005

STATUS

approved

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Last modified December 6 19:22 EST 2019. Contains 329809 sequences. (Running on oeis4.)