a(n) = Sum_{k=0..n} 9^k * binomial(n/3+k-1,k) * binomial(n-1,n-k).
A378552
a(n) = Sum_{k=0..n} 9^k * binomial(n/3+k-1,k) * binomial(n-1,n-k).
Terms
- a(0) =1a(1) =3a(2) =51a(3) =900a(4) =16455a(5) =307833a(6) =5850000a(7) =112445112a(8) =2180050215a(9) =42552000000a(10) =835075676361
External references
- oeis: A378552