a(n) = Sum_{k=0..n} (-1)^k * binomial(3*n-k+1,n-k).
A390543
a(n) = Sum_{k=0..n} (-1)^k * binomial(3*n-k+1,n-k).
Terms
- a(0) =1a(1) =3a(2) =16a(3) =91a(4) =541a(5) =3300a(6) =20476a(7) =128603a(8) =815083a(9) =5202523a(10) =33394208a(11) =215340628a(12) =1393938716a(13) =9052470696a(14) =58951457956a(15) =384826276443
External references
- oeis: A390543