a(n) = Sum_{k=0..n} Sum_{j=0..k} (binomial(n,k) * binomial(k,j))^n.
A336270
a(n) = Sum_{k=0..n} Sum_{j=0..k} (binomial(n,k) * binomial(k,j))^n.
Terms
- a(0) =1a(1) =3a(2) =15a(3) =381a(4) =67635a(5) =83118753a(6) =813824623689
External references
- oeis: A336270