G.f.: Sum_{n>=0} x^n * Sum_{k=0..n} binomial(n,k)^2 * x^k/(1-4*x)^k.
A217666
G.f.: Sum_{n>=0} x^n * Sum_{k=0..n} binomial(n,k)^2 * x^k/(1-4*x)^k.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =9a(4) =43a(5) =198a(6) =903a(7) =4121a(8) =18840a(9) =86255a(10) =395397a(11) =1814662a(12) =8337729a(13) =38350063a(14) =176574336a(15) =813785593a(16) =3753980313a(17) =17332179596a(18) =80089232683a(19) =370370470791
External references
- oeis: A217666