Convolution of natural numbers >= 2 and the partition numbers (A000041).

Terms

a(0) =2a(1) =5a(2) =11a(3) =21a(4) =38a(5) =64a(6) =105a(7) =165a(8) =254a(9) =381a(10) =562a(11) =813a(12) =1162a(13) =1636a(14) =2279a(15) =3139a(16) =4285a(17) =5794a(18) =7776a(19) =10353a(20) =13694a(21) =17992a(22) =23502a(23) =30520a(24) =39433a(25) =50687a(26) =64855a(27) =82607a(28) =104785a(29) =132375