A nonlinear recurrence.

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =3a(5) =4a(6) =5a(7) =7a(8) =9a(9) =11a(10) =14a(11) =18a(12) =23a(13) =29a(14) =38a(15) =47a(16) =59a(17) =76a(18) =95a(19) =120a(20) =154a(21) =191a(22) =241a(23) =310a(24) =383a(25) =483a(26) =620a(27) =767a(28) =968a(29) =1242