Convolution of nonzero triangular numbers (A000217) and nonzero tetradecagonal numbers (A051866).

Terms

a(0) =1a(1) =17a(2) =87a(3) =287a(4) =742a(5) =1638a(6) =3234a(7) =5874a(8) =9999a(9) =16159a(10) =25025a(11) =37401a(12) =54236a(13) =76636a(14) =105876a(15) =143412a(16) =190893a(17) =250173a(18) =323323a(19) =412643a(20) =520674a(21) =650210a(22) =804310a(23) =986310a(24) =1199835a(25) =1448811a(26) =1737477a(27) =2070397a(28) =2452472a(29) =2888952