A292764(n)/2.

Terms

a(0) =1a(1) =4a(2) =9a(3) =18a(4) =33a(5) =60a(6) =105a(7) =180a(8) =309a(9) =526a(10) =895a(11) =1520a(12) =2581a(13) =4378a(14) =7427a(15) =12596