E.g.f. = exp(-x*(x+4)/2)/(1-x)^3.

Terms

a(0) =1a(1) =1a(2) =3a(3) =13a(4) =67a(5) =423a(6) =3133a(7) =26479a(8) =251529a(9) =2651041a(10) =30680659a(11) =386635269a(12) =5268724987a(13) =77182895047