OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..500
FORMULA
MATHEMATICA
PROG
(PARI) {a(n)=local(X=x+x*O(x^n)); sum(k=0, n, polcoeff(polcoeff((1-2*X)/(1-X-X*y*(1-2*X)), n, x), k, y)^2)}
(Sage)
@cached_function
def A104967(n, k): return sum( (-2)^j*binomial(k+1, j)*binomial(n-j, k) for j in (0..n-k))
[A104969(n) for n in (0..50)] # G. C. Greubel, Jun 09 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Mar 30 2005
STATUS
approved