a(n) = self-convolution of row n of array T given by A027926.

Terms

a(0) =1a(1) =3a(2) =10a(3) =33a(4) =105a(5) =324a(6) =977a(7) =2895a(8) =8462a(9) =24465a(10) =70101a(11) =199368a(12) =563425a(13) =1583643a(14) =4430290a(15) =12342849a(16) =34262337a(17) =94800780a(18) =261545777a(19) =719697255a(20) =1975722326a(21) =5412138033a(22) =14796520365a(23) =40380240528a(24) =110016825025a(25) =299285288499a(26) =813011578522