G.f.: Sum_{n>=0} x^n / (1-x^2)^(2*n+1) * [Sum_{k=0..n} C(n,k)^2 * x^k] * [Sum_{k=0..n} C(n,k)^2 * x^(2*k)].
A246653
G.f.: Sum_{n>=0} x^n / (1-x^2)^(2*n+1) * [Sum_{k=0..n} C(n,k)^2 * x^k] * [Sum_{k=0..n} C(n,k)^2 * x^(2*k)].
Terms
- a(0) =1a(1) =1a(2) =3a(3) =9a(4) =25a(5) =87a(6) =287a(7) =993a(8) =3519a(9) =12525a(10) =45369a(11) =165519a(12) =608569a(13) =2253307a(14) =8386575a(15) =31370297a(16) =117834837a(17) =444258387a(18) =1680516731a(19) =6375706325a(20) =24253227159a(21) =92481509389a(22) =353417696625
External references
- oeis: A246653