a(n) = Sum_{k=0..n} (4*k+1) * binomial(3*n+k+1,n-k)/(3*n+k+1).
A390519
a(n) = Sum_{k=0..n} (4*k+1) * binomial(3*n+k+1,n-k)/(3*n+k+1).
Terms
- a(0) =1a(1) =2a(2) =9a(3) =47a(4) =262a(5) =1516a(6) =8988a(7) =54213a(8) =331233a(9) =2044151a(10) =12716872a(11) =79636493a(12) =501466519a(13) =3172569392a(14) =20152910577a(15) =128468322235a(16) =821489663702
External references
- oeis: A390519