Number of base-3 pyramids of height n.

Terms

a(0) =2a(1) =2a(2) =2a(3) =6a(4) =10a(5) =14a(6) =30a(7) =47a(8) =62a(9) =91a(10) =134a(11) =217a(12) =316a(13) =483a(14) =743a(15) =1118a(16) =1598a(17) =2422a(18) =3616a(19) =5316a(20) =8061a(21) =12284a(22) =18675a(23) =26946a(24) =39146a(25) =59339a(26) =90790a(27) =137602a(28) =206390a(29) =316184