a(n) = Sum_{k=0..floor(n/3)} (-1)^k * (4*k+1) * binomial(3*n-5*k+1,n-3*k)/(3*n-5*k+1).
A390517
a(n) = Sum_{k=0..floor(n/3)} (-1)^k * (4*k+1) * binomial(3*n-5*k+1,n-3*k)/(3*n-5*k+1).
Terms
- a(0) =1a(1) =1a(2) =3a(3) =11a(4) =50a(5) =248a(6) =1299a(7) =7061a(8) =39450a(9) =225137a(10) =1306767a(11) =7690437a(12) =45782244a(13) =275209123a(14) =1668175785a(15) =10184733820a(16) =62573930785a(17) =386589267790
External references
- oeis: A390517