a(n) = A079137(n)/2.

Terms

a(0) =0a(1) =0a(2) =4a(3) =0a(4) =41a(5) =372a(6) =3189a(7) =15544a(8) =94844a(9) =606556a(10) =3341926a(11) =18243164a(12) =100641235a(13) =541792652a(14) =2853058729a(15) =14909615644a(16) =77215251362a(17) =395393899688