a(n) = Sum_{k=0..floor(n/3)} binomial(3*n-2*k,n-3*k).
A371754
a(n) = Sum_{k=0..floor(n/3)} binomial(3*n-2*k,n-3*k).
Terms
- a(0) =1a(1) =3a(2) =15a(3) =85a(4) =505a(5) =3081a(6) =19125a(7) =120173a(8) =761995a(9) =4865697a(10) =31244029a(11) =201544551a(12) =1305039209a(13) =8477521051a(14) =55221311565a(15) =360559717807
External references
- oeis: A371754