a(n) = (Sum_{j=1..3} StirlingS1(3,j)*(2^j-1)^n)/3!.

A341590

a(n) = (Sum_{j=1..3} StirlingS1(3,j)*(2^j-1)^n)/3!.

Terms

    a(0) =0a(1) =0a(2) =4a(3) =44a(4) =360a(5) =2680a(6) =19244a(7) =136164a(8) =957520a(9) =6715760a(10) =47049684a(11) =329465884a(12) =2306615480a(13) =16147371240a(14) =113034787324a(15) =791253077204

External references