Primes p such that p-1 and p+1 have two distinct prime factors.

Terms

a(0) =11a(1) =13a(2) =19a(3) =23a(4) =37a(5) =47a(6) =53a(7) =73a(8) =97a(9) =107a(10) =163a(11) =193a(12) =383a(13) =487a(14) =577a(15) =863a(16) =1153a(17) =2593a(18) =2917a(19) =4373a(20) =8747a(21) =995327a(22) =1492993a(23) =1990657a(24) =5308417a(25) =28311553a(26) =86093443a(27) =6879707137