a(n) = ceiling(n*exp(n)).

Terms

a(0) =0a(1) =3a(2) =15a(3) =61a(4) =219a(5) =743a(6) =2421a(7) =7677a(8) =23848a(9) =72928a(10) =220265a(11) =658616a(12) =1953058a(13) =5751375a(14) =16836460a(15) =49035261a(16) =142177769a(17) =410634197a(18) =1181879445a(19) =3391163719a(20) =9703303909a(21) =27695130425a(22) =78868082615a(23) =224130479264a(24) =635738931117