a(n) = floor(8^n/3^n).

Terms

a(0) =1a(1) =2a(2) =7a(3) =18a(4) =50a(5) =134a(6) =359a(7) =958a(8) =2557a(9) =6818a(10) =18183a(11) =48490a(12) =129307a(13) =344820a(14) =919522a(15) =2452059a(16) =6538825a(17) =17436866a(18) =46498311a(19) =123995496a(20) =330654658a(21) =881745755a(22) =2351322014a(23) =6270192038a(24) =16720512102a(25) =44588032273a(26) =118901419396