a(n) = (3*a(n-1)) XOR a(n-2).

Terms

a(0) =0a(1) =1a(2) =3a(3) =8a(4) =27a(5) =89a(6) =272a(7) =873a(8) =2859a(9) =8936a(10) =25491a(11) =67665a(12) =228192a(13) =752241a(14) =2167859a(15) =6833896a(16) =18464907a(17) =52758345a(18) =142005584a(19) =440498361a(20) =1186119547a(21) =3461957320a(22) =9357060899a(23) =26968655777a(24) =72945663424a(25) =226371206881a(26) =613739200867