G.f. satisfies: A(x) = exp( Sum_{n>=1} [Sum_{k=0..2*n} A200536(n,2*n-k)^2 * x^k] / A(x)^n * x^n/n ), where A200536(n,2*n-k) is the coefficient of x^k in (2+3*x+x^2)^n.
A251689
G.f. satisfies: A(x) = exp( Sum_{n>=1} [Sum_{k=0..2*n} A200536(n,2*n-k)^2 * x^k] / A(x)^n * x^n/n ), where A200536(n,2*n-k) is the coefficient of x^k in (2+3*x+x^2)^n.
Terms
- a(0) =1a(1) =4a(2) =9a(3) =37a(4) =40a(5) =153a(6) =144a(7) =468a(8) =432a(9) =1260a(10) =1152a(11) =3168a(12) =2880a(13) =7632a(14) =6912a(15) =17856a(16) =16128a(17) =40896a(18) =36864a(19) =92160a(20) =82944a(21) =205056a(22) =184320a(23) =451584a(24) =405504a(25) =986112a(26) =884736a(27) =2138112a(28) =1916928a(29) =4608000
External references
- oeis: A251689