a(n) = [x^(2*n)] S(x)^n, where S(x) = (1 - x - sqrt(1 - 6*x + x^2))/(2*x) is the o.g.f. of the large Schröder numbers A006318.
A333482
a(n) = [x^(2*n)] S(x)^n, where S(x) = (1 - x - sqrt(1 - 6*x + x^2))/(2*x) is the o.g.f. of the large Schröder numbers A006318.
Terms
- a(0) =1a(1) =6a(2) =304a(3) =17718a(4) =1093760a(5) =69690006a(6) =4530426640a(7) =298634382374
External references
- oeis: A333482