a(n) = Sum_{k=0..n} C(n,k)*3^[k*(k-1)/2].

A135755

a(n) = Sum_{k=0..n} C(n,k)*3^[k*(k-1)/2].

Terms

    a(0) =1a(1) =2a(2) =6a(3) =40a(4) =860a(5) =63000a(6) =14714728a(7) =10562062112

External references