Smallest prime factor of 3^n+1 having the form 2*k*n+1.

Terms

a(0) =5a(1) =7a(2) =41a(3) =61a(4) =73a(5) =547a(6) =17a(7) =19a(8) =1181a(9) =67a(10) =6481a(11) =398581a(12) =29a(13) =31a(14) =21523361a(15) =103a(16) =73a(17) =2851a(18) =41a(19) =43a(20) =5501a(21) =23535794707a(22) =97a(23) =151a(24) =53a(25) =19441a(26) =430697a(27) =523a(28) =47763361a(29) =6883