a(n) = T(3,n), array T given by A048505.

Terms

a(0) =1a(1) =17a(2) =58a(3) =160a(4) =408a(5) =1000a(6) =2392a(7) =5624a(8) =13048a(9) =29944a(10) =68088a(11) =153592a(12) =344056a(13) =765944a(14) =1695736a(15) =3735544a(16) =8191992a(17) =17891320a(18) =38928376a(19) =84410360a(20) =182452216a(21) =393215992a(22) =845152248a(23) =1811939320a(24) =3875536888a(25) =8271167480a(26) =17616076792a(27) =37446746104a(28) =79456894968a(29) =168309030904