OFFSET
1,2
PROG
(PARI) a(n) = {polcoef(polcoef(prod(j=1, n, prod(k=1, n, 1 + 'x^(2*k-n-1)*'y^(2*j-n-1) )), 0), 0)/2} \\ Andrew Howroyd, Jan 07 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 25 2007
EXTENSIONS
a(12)-a(13) from Andrew Howroyd, Jan 07 2023
STATUS
approved