OFFSET
0,3
COMMENTS
a(n) = A323690(n*(n+1)).
LINKS
Paul D. Hanna, Table of n, a(n) for n = 0..100
EXAMPLE
The generating function of A323690 is
G(x) = Sum_{n>=0} (x^(n+1) + i)^n / (1 + i*x^n)^(n+1),
in which the constant term is taken to be 1, so that
G(x) = 1 + 2*x + x^2 - 8*x^3 + 18*x^5 + 11*x^6 - 16*x^7 - 44*x^8 + 36*x^10 - 12*x^11 + 35*x^12 + 112*x^13 + 56*x^14 - 144*x^15 - 260*x^16 - 88*x^17 + 48*x^18 - 20*x^19 + 95*x^20 + 504*x^21 + 636*x^22 + 288*x^23 - 578*x^24 - 1016*x^25 - 292*x^26 - 216*x^27 - 624*x^28 - 210*x^29 + 73*x^30 + ...
This sequence gives the odd coefficients of x^n, which occur at n = k*(k+1) for k >= 0.
PROG
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Feb 13 2019
STATUS
approved