a(n) = Sum_{k=0..floor(n/3)} (-1)^k * binomial(4*n-3*k-1,n-3*k).
A371817
a(n) = Sum_{k=0..floor(n/3)} (-1)^k * binomial(4*n-3*k-1,n-3*k).
Terms
- a(0) =1a(1) =3a(2) =21a(3) =164a(4) =1353a(5) =11508a(6) =99808a(7) =877425a(8) =7790745a(9) =69704921a(10) =627438606a(11) =5675535000a(12) =51546958296a(13) =469764721533
External references
- oeis: A371817