Convolution of A073709, which is also the first differences of the unique terms of A073709.

Terms

a(0) =1a(1) =2a(2) =7a(3) =12a(4) =35a(5) =58a(6) =133a(7) =208a(8) =450a(9) =692a(10) =1358a(11) =2024a(12) =3822a(13) =5620a(14) =10018a(15) =14416a(16) =25025a(17) =35634a(18) =59591a(19) =83548a(20) =136955a(21) =190362a(22) =303725a(23) =417088a(24) =655128a(25) =893168a(26) =1374632a(27) =1856096a(28) =2820456a(29) =3784816