a(n) = A153801(n)/2.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =2a(6) =1a(7) =6a(8) =19a(9) =30a(10) =38a(11) =45a(12) =240a(13) =282a(14) =616a(15) =1075a(16) =1111a(17) =1578a(18) =2093a(19) =2176a(20) =4808a(21) =4931a(22) =5565a(23) =9924a(24) =10802a(25) =11554a(26) =22197a(27) =43068a(28) =55197a(29) =65968