a(n) = P_n(9), where P_n is n-th Legendre polynomial; also, a(n) = central coefficient of (1 + 9*x + 20*x^2)^n.
A084769
a(n) = P_n(9), where P_n is n-th Legendre polynomial; also, a(n) = central coefficient of (1 + 9*x + 20*x^2)^n.
Terms
- a(0) =1a(1) =9a(2) =121a(3) =1809a(4) =28401a(5) =458649a(6) =7544041a(7) =125700129a(8) =2114588641a(9) =35836273449a(10) =610897146201
External references
- oeis: A084769