A370549 - OEIS

A370549

a(n) is the numerator of the imaginary part of Product_{k=1..n} (1/k + i) where i is the imaginary unit.

1, 3, 0, -5, -3, 35, 11, -65, -3055, 4433, 2561, -18863, -614635, 14705, 3871801, -6702403, -23794993, -21392575, 1677354925, 2206770805, -30432904645, -617315066615, 2099373575975, 551582580432325, -11053607615333933, -180184164588301, 4198057769186443, 435884809756010315

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..28.

FORMULA

a(n) = numerator of A105751(n)/n!. - Chai Wah Wu, Feb 22 2024

EXAMPLE

See A370547.

PROG

(PARI) a370549(n) = numerator(imag(prod(k=1, n, 1/k+I)))

(Python)

from math import factorial, gcd

from sympy.functions.combinatorial.numbers import stirling

def A370549(n): return (a:=sum(stirling(n+1, n-(k<<1), kind=1)*(-1 if k&1 else 1) for k in range((n>>1)+1)))//gcd(a, factorial(n)) # Chai Wah Wu, Feb 22 2024

CROSSREFS

Cf. A105751, A370547, A370548, A370550.

Sequence in context: A275393 A029840 A144670 * A011078 A354592 A259617

Adjacent sequences: A370546 A370547 A370548 * A370550 A370551 A370552

KEYWORD

frac,sign,easy

AUTHOR

Hugo Pfoertner, Feb 22 2024

STATUS

approved