%I A122783
%S A122783 1,6,10,15,21,30,35,105,185,190,217,231,301,430,435,481,561,777,1105,
%T A122783 1111,1221,1261,1333,1729,1866,2121,2465,2553,2701,2821,2955,3421,3565,
%U A122783 3589,3885,3913,4123,4495,5061,5565,5662,5713,6531,6533,6601
%N A122783 Nonprimes n such that 6^n==6 (mod n).
%C A122783 Theorem: If both numbers q and 2q-1 are primes then n=q*(2q-1) is in 
               the sequence iff q<5 or q is of the form 12k+1. 6,15,2701,18721,49141,
               104653,226801,665281,... are such terms.
%t A122783 Select[Range[7000], ! PrimeQ[ # ] && Mod[6^#, # ] == Mod[6, # ] &]
%Y A122783 Cf. A005937.
%Y A122783 Sequence in context: A157937 A080255 A115744 this_sequence A124000 A068443 
               A113940
%Y A122783 Adjacent sequences: A122780 A122781 A122782 this_sequence A122784 A122785 
               A122786
%K A122783 easy,nonn
%O A122783 1,2
%A A122783 Farideh Firoozbakht (mymontain(AT)yahoo.com), Sep 12 2006