a(n) is the constant term in the expansion of Product_{k=1..n} (x^k + 1/x^k)^4.

A124996

a(n) is the constant term in the expansion of Product_{k=1..n} (x^k + 1/x^k)^4.

Terms

    a(0) =1a(1) =6a(2) =44a(3) =426a(4) =4658a(5) =55260a(6) =689508a(7) =8914872a(8) =118374410a(9) =1604658420a(10) =22115171280a(11) =308940507202

External references