a(n) = A008893(n)/2.

Terms

a(0) =0a(1) =4a(2) =33a(3) =129a(4) =355a(5) =795a(6) =1554a(7) =2758a(8) =4554a(9) =7110a(10) =10615a(11) =15279a(12) =21333a(13) =29029a(14) =38640a(15) =50460a(16) =64804a(17) =82008a(18) =102429a(19) =126445a(20) =154455a(21) =186879a(22) =224158a(23) =266754a(24) =315150a(25) =369850a(26) =431379a(27) =500283a(28) =577129a(29) =662505