a(n) = Sum_{k=0..n} (-1)^k * binomial(3*n-k-1,n-k).
A371813
a(n) = Sum_{k=0..n} (-1)^k * binomial(3*n-k-1,n-k).
Terms
- a(0) =1a(1) =1a(2) =7a(3) =40a(4) =239a(5) =1461a(6) =9076a(7) =57044a(8) =361711a(9) =2309467a(10) =14827487a(11) =95630272a(12) =619111172a(13) =4021011580a(14) =26187682024a(15) =170960159100
External references
- oeis: A371813