Where 3^n occurs in n-almost primes, starting at a(0)=1.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =8a(5) =14a(6) =23a(7) =39a(8) =64a(9) =103a(10) =169a(11) =269a(12) =427a(13) =676a(14) =1065a(15) =1669a(16) =2628a(17) =4104a(18) =6414a(19) =10023a(20) =15608a(21) =24281a(22) =37733a(23) =58503a(24) =90616a(25) =140187a(26) =216625a(27) =334527a(28) =516126a(29) =795632