Infinitesimal generator of x*(x + 1).

Terms

a(0) =1a(1) =1a(2) =3a(3) =16a(4) =124a(5) =1256a(6) =15576a(7) =226248a(8) =3729216a(9) =68179968a(10) =1361836800a(11) =29501349120a(12) =693638208000