a(n) = T(n,n-3), array T as in A038738.

Terms

a(0) =1a(1) =9a(2) =47a(3) =188a(4) =643a(5) =1993a(6) =5798a(7) =16193a(8) =44068a(9) =118013a(10) =312974a(11) =825277a(12) =2169045a(13) =5690426a(14) =14913861a(15) =39066661a(16) =102306471a(17) =267879086a(18) =701364436a(19) =1836256726a(20) =4807458872a(21) =12586185670a(22) =32951178868a(23) =86267449214a(24) =225851287529