a(n) = n! * (n + 1 + 2*Sum_{k=1...n} 1/k).

Terms

a(0) =1a(1) =4a(2) =12a(3) =46a(4) =220a(5) =1268a(6) =8568a(7) =66456a(8) =582048a(9) =5681952a(10) =61174080a(11) =720089280a(12) =9199906560a(13) =126783809280