OFFSET
1,2
FORMULA
G.f.: 1/(1-x*B(x)^2*y)-1, where B(x) is g.f. of A027307.
G.f. satisfies A(x)=x*[(1+A(x))/(1-A(x))]^2.
EXAMPLE
1;
4, 1;
24, 8, 1;
172, 64, 12, 1;
1360, 536, 120, 16, 1;
PROG
(Maxima)
T(n, k):=(k*sum(binomial(2*n, n-k-i)*binomial(2*n+i-1, i), i, 0, n-k))/n;
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Vladimir Kruchinin, Apr 28 2015
STATUS
approved