G.f.: A(x,y) = Sum_{n>=0} n!*x^n*y^n * Product_{k=1..n} (1+y + 2*k*x*y) / (1 + (1+y)*k*x + 2*k^2*x^2*y).
A221987
G.f.: A(x,y) = Sum_{n>=0} n!*x^n*y^n * Product_{k=1..n} (1+y + 2*k*x*y) / (1 + (1+y)*k*x + 2*k^2*x^2*y).
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =4a(5) =1a(6) =1a(7) =11a(8) =11a(9) =1a(10) =1a(11) =26a(12) =62a(13) =26a(14) =1a(15) =1a(16) =57a(17) =274a(18) =274a(19) =57a(20) =1a(21) =1a(22) =120a(23) =1063a(24) =2024a(25) =1063a(26) =120a(27) =1a(28) =1a(29) =247
External references
- oeis: A221987