OFFSET
0,4
COMMENTS
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..500
FORMULA
a(n) = Im(Sum{k=0..n, C(floor((n+k)/2),k)*I^k*A000108(k)}), I=sqrt(-1).
MATHEMATICA
Table[Im[Sum[I^k*Binomial[2*k, k]*Binomial[Floor[(n + k)/2], k]/(k + 1), {k, 0, n}]], {n, 0, 50}] (* G. C. Greubel, Feb 21 2018 *)
PROG
(PARI) for(n=0, 50, print1(imag(sum(k=0, n, I^k*binomial(2*k, k)* binomial( floor((n+k)/2), k)/(k+1) )), ", ")) \\ G. C. Greubel, Feb 21 2018
(Magma) [Round(Imaginary((&+[(Sqrt(-1))^k*Binomial(2*k, k)*Binomial( Floor((n+k)/2), k)/(k+1): k in [0..n]]))): n in [0..30]]; // G. C. Greubel, Feb 21 2018
CROSSREFS
KEYWORD
sign
AUTHOR
Paul Barry, Jan 07 2011
STATUS
approved