(Terms in A028266)/2.

Terms

a(0) =2a(1) =2a(2) =4a(3) =3a(4) =3a(5) =13a(6) =4a(7) =13a(8) =13a(9) =4a(10) =17a(11) =45a(12) =17a(13) =5a(14) =5a(15) =74a(16) =133a(17) =161a(18) =133a(19) =74a(20) =6a(21) =32a(22) =207a(23) =294a(24) =294a(25) =207a(26) =32a(27) =6a(28) =38a(29) =501