a(n) = nextprime(3^n)-3^n.

Terms

a(0) =1a(1) =2a(2) =2a(3) =2a(4) =2a(5) =8a(6) =4a(7) =16a(8) =2a(9) =4a(10) =2a(11) =20a(12) =16a(13) =8a(14) =2a(15) =2a(16) =26a(17) =34a(18) =10a(19) =56a(20) =8a(21) =56a(22) =4a(23) =32a(24) =2a(25) =14a(26) =2a(27) =16a(28) =26a(29) =130