Convolution of A000041 and A000290.

Terms

a(0) =0a(1) =1a(2) =5a(3) =15a(4) =36a(5) =76a(6) =147a(7) =267a(8) =462a(9) =769a(10) =1240a(11) =1947a(12) =2988a(13) =4496a(14) =6649a(15) =9683a(16) =13909a(17) =19734a(18) =27686a(19) =38447a(20) =52892a(21) =72138a(22) =97604a(23) =131084a(24) =174835a(25) =231687a(26) =305173a(27) =399687a(28) =520675a(29) =674865