Unbranched catafusenes, unsymmetrical.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =4a(5) =16a(6) =50a(7) =158a(8) =472a(9) =1406a(10) =4111a(11) =11998a(12) =34781a(13) =100660a(14) =290464a(15) =837137a(16) =2408914a(17) =6925100a(18) =19888057a(19) =57071610