a(n) = T(n,n-6), array T as in A055807.

Terms

a(0) =1a(1) =63a(2) =192a(3) =432a(4) =832a(5) =1452a(6) =2364a(7) =3653a(8) =5418a(9) =7773a(10) =10848a(11) =14790a(12) =19764a(13) =25954a(14) =33564a(15) =42819a(16) =53966a(17) =67275a(18) =83040a(19) =101580a(20) =123240a(21) =148392a(22) =177436a(23) =210801a(24) =248946a(25) =292361a(26) =341568a(27) =397122a(28) =459612a(29) =529662