Smallest prime of the form k^n + k^(n-1) - 1.

Terms

a(0) =2a(1) =5a(2) =11a(3) =23a(4) =47a(5) =971a(6) =191a(7) =383a(8) =22136835839a(9) =1310719a(10) =2259801991a(11) =6143a(13) =91424858111a(15) =57395627a(16) =21474836479a(18) =786431