a(n) = Sum_{k=0..n} T(k)*T(n-k), where T is A000073; convolution of A000073 with itself.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =2a(6) =5a(7) =12a(8) =26a(9) =56a(10) =118a(11) =244a(12) =499a(13) =1010a(14) =2027a(15) =4040a(16) =8004a(17) =15776a(18) =30956a(19) =60504a(20) =117845a(21) =228818a(22) =443057a(23) =855732a(24) =1649022a(25) =3171128a(26) =6086626a(27) =11662252a(28) =22309543a(29) =42614178