Denominator of Sum_{k=0..n} n^k/k!.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =12a(5) =5a(6) =72a(7) =315a(8) =2240a(9) =567a(10) =1814400a(11) =77a(12) =239500800a(13) =868725a(14) =7175168a(15) =49116375a(17) =14889875a(19) =14849255421