Threefold convolution of A004148 (the RNA secondary structure numbers) with itself.

Terms

a(0) =1a(1) =3a(2) =6a(3) =13a(4) =30a(5) =69a(6) =160a(7) =375a(8) =885a(9) =2102a(10) =5022a(11) =12060a(12) =29095a(13) =70485a(14) =171399a(15) =418220a(16) =1023663a(17) =2512761a(18) =6184253a(19) =15257262a(20) =37725972a(21) =93477778a(22) =232069116a(23) =577179078a(24) =1437926977a(25) =3587977293a(26) =8966170056a(27) =22437282917a(28) =56221762626a(29) =141051397725