Convolution of A000217 and A001045.

Terms

a(0) =0a(1) =0a(2) =1a(3) =4a(4) =12a(5) =30a(6) =69a(7) =150a(8) =316a(9) =652a(10) =1329a(11) =2688a(12) =5412a(13) =10866a(14) =21781a(15) =43618a(16) =87300a(17) =174672a(18) =349425a(19) =698940a(20) =1397980a(21) =2796070a(22) =5592261a(23) =11184654a(24) =22369452a(25) =44739060a(26) =89478289a(27) =178956760a(28) =357913716a(29) =715827642