a(n) = 3^n + 1 - 0^n.

Terms

a(0) =1a(1) =4a(2) =10a(3) =28a(4) =82a(5) =244a(6) =730a(7) =2188a(8) =6562a(9) =19684a(10) =59050a(11) =177148a(12) =531442a(13) =1594324a(14) =4782970a(15) =14348908a(16) =43046722a(17) =129140164a(18) =387420490a(19) =1162261468a(20) =3486784402a(21) =10460353204a(22) =31381059610a(23) =94143178828a(24) =282429536482a(25) =847288609444