Composite numbers n such that b^(n+1) == 1 (mod n) for every b coprime to n.

Terms

a(0) =15a(1) =35a(2) =255a(3) =455a(4) =1295a(5) =2703a(6) =4355a(7) =6479a(8) =9215a(9) =10439a(10) =11951a(11) =16211a(12) =23435a(13) =27839a(14) =44099a(15) =47519a(16) =47879a(17) =62567a(18) =63167a(19) =65535a(20) =93023a(21) =94535a(22) =104195a(23) =120959a(24) =131327a(25) =133055a(26) =141155a(27) =142883a(28) =157079a(29) =170819