a(2*n) = 3*a(2*n-1) - 1, a(2*n+1) = 3*a(2*n), with a(1)=1.

Terms

a(0) =1a(1) =2a(2) =6a(3) =17a(4) =51a(5) =152a(6) =456a(7) =1367a(8) =4101a(9) =12302a(10) =36906a(11) =110717a(12) =332151a(13) =996452a(14) =2989356a(15) =8968067a(16) =26904201a(17) =80712602a(18) =242137806a(19) =726413417a(20) =2179240251a(21) =6537720752a(22) =19613162256a(23) =58839486767a(24) =176518460301a(25) =529555380902