a(n) = A322893(n) / (n*(n+1)/2), where A322893(n) = [x^(n-1)] Product_{k=1..n} (k + x + 2*k*x^2), for n >= 1.
A322894
a(n) = A322893(n) / (n*(n+1)/2), where A322893(n) = [x^(n-1)] Product_{k=1..n} (k + x + 2*k*x^2), for n >= 1.
Terms
- a(0) =1a(1) =1a(2) =7a(3) =31a(4) =411a(5) =3571a(6) =69581a(7) =927837a(8) =23794485a(9) =433057989a(10) =13747956267a(11) =319028238387
External references
- oeis: A322894