a(n) = Sum_{k=0..n} 3^k * binomial(n+2,k) * binomial(n+2,k+2).
A387339
a(n) = Sum_{k=0..n} 3^k * binomial(n+2,k) * binomial(n+2,k+2).
Terms
- a(0) =1a(1) =12a(2) =108a(3) =880a(4) =6855a(5) =52164a(6) =391720a(7) =2918304a(8) =21634290a(9) =159880600a(10) =1179180552a(11) =8685874080a(12) =63930198787a(13) =470327654580
External references
- oeis: A387339