a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(3*k+1,k).
A390541
a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(3*k+1,k).
Terms
- a(0) =1a(1) =3a(2) =18a(3) =102a(4) =613a(5) =3755a(6) =23377a(7) =147167a(8) =934408a(9) =5972492a(10) =38379673a(11) =247718087a(12) =1604764909a(13) =10428457971a(14) =67950502389a(15) =443788258155
External references
- oeis: A390541