Odd prime powers p^w (w>1) such that p^w+2 is prime.

Terms

a(0) =9a(1) =27a(2) =81a(3) =125a(4) =6561a(5) =24389a(6) =59049a(7) =161051a(8) =357911a(9) =571787a(10) =1442897a(11) =4782969a(12) =5177717a(13) =14348907a(14) =18191447a(15) =30080231a(16) =73560059a(17) =80062991a(18) =118370771a(19) =127263527a(20) =131872229a(21) =318611987a(22) =344472101a(23) =440711081a(24) =461889917a(25) =590589719a(26) =756058031a(27) =865523177