a(n) = Sum_{k=0..n} C(n,k) * (2^k + 3^k)^(n-k).
A251661
a(n) = Sum_{k=0..n} C(n,k) * (2^k + 3^k)^(n-k).
Terms
- a(0) =1a(1) =3a(2) =15a(3) =123a(4) =1671a(5) =37863a(6) =1447515a(7) =93965763a(8) =10456301871
External references
- oeis: A251661
A251661
a(n) = Sum_{k=0..n} C(n,k) * (2^k + 3^k)^(n-k).