OFFSET
0,2
COMMENTS
FORMULA
a(n) = (n+3)*(3*(n+6)*2^(2*n+3)-(n+4)*binomial(2*n+7, n+3))/12; G.f. (c(x)^2)/(1-4*x)^3, where c(x) = g.f. for Catalan numbers.
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
STATUS
approved