Self-convolution omits 1's at positions of triangular numbers less one.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =1a(6) =6a(7) =11a(8) =12a(9) =1a(10) =24a(11) =48a(12) =71a(13) =78a(14) =1a(15) =155a(16) =272a(17) =420a(18) =652a(19) =903a(20) =1a(21) =1364a(22) =2144a(23) =3436a(24) =5955a(25) =9668a(26) =10838a(27) =1a(28) =16408a(29) =27948