a(n) = Sum_{i+j+k=n, 0<=i<=j<=k<=n} (2n)!/((i+j)! * (j+k)! * (k+i)!).

A092473

a(n) = Sum_{i+j+k=n, 0<=i<=j<=k<=n} (2n)!/((i+j)! * (j+k)! * (k+i)!).

Terms

    a(0) =1a(1) =2a(2) =18a(3) =170a(4) =1330a(5) =11382a(6) =117810a(7) =934362a(8) =8611746a(9) =82240730a(10) =699393838a(11) =6244164940a(12) =59910383026a(13) =507902083210

External references