12 Mar
2018
12 Mar
'18
1:37 p.m.
https://oeis.org/A077816 , e.g., In[19]:= Select[Range@9999, Mod[2^EulerPhi@#, #^2] == 1 &] Out[19]= {1093, 3279, 3511, 7651} A different definition might be In[18]:= Select[Range@999999, Mod[2^#, #^2] == 2 &] Out[18]= {1093, 3511} No mention of primes! https://oeis.org/A001220 Arthur Wieferich showed that if p is not a term of this sequence, then the First Case of Fermat's Last Theorem has no solution in x, y and z for prime exponent p (cf. Wieferich, 1909). - Felix Fröhlich <https://oeis.org/wiki/User:Felix_Fröhlich>, May 27 2016 --rwg