a(n) = Sum_{k=0..2*n} (n - floor(k/2))^k.

A099556

a(n) = Sum_{k=0..2*n} (n - floor(k/2))^k.

Terms

    a(0) =1a(1) =2a(2) =5a(3) =18a(4) =91a(5) =604a(6) =5123a(7) =53808a(8) =679389a(9) =10107934a(10) =174544505a(11) =3451802006a(12) =77302457079

External references