T(n,n+3), T given by A027960.

Terms

a(0) =1a(1) =6a(2) =19a(3) =47a(4) =101a(5) =199a(6) =370a(7) =661a(8) =1148a(9) =1954a(10) =3278a(11) =5442a(12) =8967a(13) =14696a(14) =23993a(15) =39065a(16) =63483a(17) =103025a(18) =167040a(19) =270655a(20) =438346a(21) =709716a(22) =1148844a(23) =1859412a(24) =3009181a(25) =4869594a(26) =7879855a(27) =12750611a(28) =20631713a(29) =33383659