G.f.: exp( Sum_{n>=0} [ Sum_{k=0..2*n} A027907(n,k)^2 * x^k ]* x^n/n ), where A027907 is the triangle of trinomial coefficients.
A186236
G.f.: exp( Sum_{n>=0} [ Sum_{k=0..2*n} A027907(n,k)^2 * x^k ]* x^n/n ), where A027907 is the triangle of trinomial coefficients.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =5a(4) =13a(5) =34a(6) =93a(7) =262a(8) =753a(9) =2198a(10) =6502a(11) =19449a(12) =58724a(13) =178739a(14) =547836a(15) =1689407a(16) =5237939a(17) =16318137a(18) =51056027a(19) =160363129a(20) =505456920a(21) =1598263936a(22) =5068483189a(23) =16116397411a(24) =51371962474a(25) =164123564499a(26) =525447953073
External references
- oeis: A186236