a(n) = A028321(n)/2.

Terms

a(0) =3a(1) =4a(2) =18a(3) =5a(4) =23a(5) =6a(6) =189a(7) =102a(8) =420a(9) =291a(10) =41a(11) =7a(12) =711a(13) =48a(14) =1551a(15) =605a(16) =8a(17) =281a(18) =4433a(19) =2574a(20) =72a(21) =9a(22) =7007a(23) =1456a(24) =81a(25) =10a(26) =39039a(27) =27924a(28) =15834a(29) =7014