a(n) = A322237(n) / (n*(n+1)/2), where A322237(n) = [x^(n-1)] Product_{k=1..n} (k + x + k*x^2), for n >= 1.
A322236
a(n) = A322237(n) / (n*(n+1)/2), where A322237(n) = [x^(n-1)] Product_{k=1..n} (k + x + k*x^2), for n >= 1.
Terms
- a(0) =1a(1) =1a(2) =4a(3) =16a(4) =126a(5) =946a(6) =11201a(7) =125609a(8) =1988645a(9) =29865749a(10) =592326527a(11) =11181850967a(12) =266546940947
External references
- oeis: A322236