OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..50
FORMULA
a(n) = 2^(n^2)*(-1)^n*Sum_{k=0..n} C(n+k,2k)*(-2)^(n-k).
a(n) = 2^(n^2)*[x^n](1-2*x)/(1+3*x+4*x^2) = 2^(n^2) *A247560(n).
MATHEMATICA
a[n_] := Sum[Binomial[n + k, 2*k]*(-2)^(n - k), {k, 0, n}]; Table[2^(n^2)*(-1)^n*a[n], {n, 0, 10}] (* G. C. Greubel, Jun 13 2016 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Nov 03 2009
STATUS
approved