Self-convolution equals A227845.

Terms

a(0) =1a(1) =1a(2) =3a(3) =11a(4) =47a(5) =215a(6) =1029a(7) =5077a(8) =25615a(9) =131455a(10) =683749a(11) =3595341a(12) =19075913a(13) =101978321a(14) =548683499a(15) =2968535115a(16) =16138308655a(17) =88107960847a(18) =482839660509