a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(3*n-2*k-2,n-2*k).
A390684
a(n) = Sum_{k=0..floor(n/2)} (-1)^k * binomial(3*n-2*k-2,n-2*k).
Terms
- a(0) =1a(1) =1a(2) =5a(3) =30a(4) =183a(5) =1131a(6) =7072a(7) =44642a(8) =283951a(9) =1817215a(10) =11688305a(11) =75493960a(12) =489332660a(13) =3181294780a(14) =20736364508a(15) =135470724410a(16) =886795497967
External references
- oeis: A390684