a(n) = n! + Sum_{i=1..n} i.

Terms

a(0) =1a(1) =2a(2) =5a(3) =12a(4) =34a(5) =135a(6) =741a(7) =5068a(8) =40356a(9) =362925a(10) =3628855a(11) =39916866a(12) =479001678a(13) =6227020891a(14) =87178291305