a(n) = Sum_{k=0..floor(n/3)} n^(n-2*k) * binomial(n-2*k,k).
A368893
a(n) = Sum_{k=0..floor(n/3)} n^(n-2*k) * binomial(n-2*k,k).
Terms
- a(0) =1a(1) =1a(2) =4a(3) =30a(4) =288a(5) =3500a(6) =51876a(7) =908607a(8) =18374656a(9) =421492491a(10) =10815040000a(11) =306944040931
External references
- oeis: A368893