Ceiling(n^2*exp(n)).

Terms

a(0) =3a(1) =30a(2) =181a(3) =874a(4) =3711a(5) =14524a(6) =53736a(7) =190782a(8) =656350a(9) =2202647a(10) =7244772a(11) =23436690a(12) =74767864a(13) =235710440a(14) =735528909a(15) =2274844294a(16) =6980781346a(17) =21273830001a(18) =64432110648a(19) =194066078164a(20) =581597738908