a(n) = (1/n)*Sum_{i=0..n-1} C(n,i)*C(n,i+1)*8^i*9^(n-i), a(0)=1.
A133309
a(n) = (1/n)*Sum_{i=0..n-1} C(n,i)*C(n,i+1)*8^i*9^(n-i), a(0)=1.
Terms
- a(0) =1a(1) =9a(2) =153a(3) =3249a(4) =77265a(5) =1968633a(6) =52546473a(7) =1450365921a(8) =41058670113
External references
- oeis: A133309