a(n) = Sum_{k=0..floor(n/2)} (-1)^k * (3*k+1) * binomial(3*n-3*k+1,n-2*k)/(3*n-3*k+1).
A389697
a(n) = Sum_{k=0..floor(n/2)} (-1)^k * (3*k+1) * binomial(3*n-3*k+1,n-2*k)/(3*n-3*k+1).
Terms
- a(0) =1a(1) =1a(2) =2a(3) =8a(4) =38a(5) =192a(6) =1014a(7) =5539a(8) =31051a(9) =177645a(10) =1033079a(11) =6088992a(12) =36293454a(13) =218393703a(14) =1324938698a(15) =8095172229a(16) =49767868166a(17) =307644770467
External references
- oeis: A389697