a(n) = Sum_{k=1..n} C(n-1,k-1) * S2(n,k) * 3^(n-k) for n>0, a(0)=1, where S2(n,k) = A048993(n,k) are Stirling numbers of the 2nd kind.

A245060

a(n) = Sum_{k=1..n} C(n-1,k-1) * S2(n,k) * 3^(n-k) for n>0, a(0)=1, where S2(n,k) = A048993(n,k) are Stirling numbers of the 2nd kind.

Terms

    a(0) =1a(1) =1a(2) =4a(3) =28a(4) =271a(5) =3172a(6) =43174a(7) =666577a(8) =11445214a(9) =215478712a(10) =4401799930a(11) =96757165012

External references