OFFSET
0,2
FORMULA
a(n) = Sum_{k=0..n^2} binomial(n^2, k) * binomial(n^2+k, k).
a(n) = [x^(n^2)] 1/sqrt(1 - 6*x + x^2).
Equals the logarithmic derivative of A228193, after ignoring the initial term.
EXAMPLE
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Aug 15 2013
STATUS
approved