T(n,3), array T as in A054134.

Terms

a(0) =2a(1) =8a(2) =31a(3) =97a(4) =264a(5) =654a(6) =1518a(7) =3366a(8) =7227a(9) =15169a(10) =31339a(11) =64043a(12) =129906a(13) =262192a(14) =527444a(15) =1058764a(16) =2122373a(17) =4250731a(18) =8508777a(19) =17026409a(20) =34063444a(21) =68139538a(22) =136294026a(23) =272605602a(24) =545231679a(25) =1090487109a(26) =2181001623