Ceiling((Pi/e)^n).

Terms

a(0) =1a(1) =2a(2) =2a(3) =2a(4) =2a(5) =3a(6) =3a(7) =3a(8) =4a(9) =4a(10) =5a(11) =5a(12) =6a(13) =7a(14) =8a(15) =9a(16) =11a(17) =12a(18) =14a(19) =16a(20) =19a(21) =21a(22) =25a(23) =28a(24) =33a(25) =38a(26) =44a(27) =50a(28) =58a(29) =67