Composite n such that n and n+2 are prime powers.

Terms

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