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%I #5 Nov 07 2017 14:42:56
%S 1,7,49,343,539,959,1309,2401,7889,16807,18851,78449,117649,142991,
%T 590773,814247,823543
%N Numbers n such that n | 10^n + 9^n + 8^n + 7^n + 6^n + 5^n + 4^n.
%t Select[ Range[ 10^6 ], Mod[ PowerMod[ 10, #, # ] + PowerMod[ 9, #, # ] + PowerMod[ 8, #, # ] + PowerMod[ 7, #, # ] + PowerMod[ 6, #, # ] + PowerMod[ 5, #, # ] + PowerMod[ 4, #, # ], # ] == 0 & ]
%t Select[Range[10^6],Mod[Plus@@Table[PowerMod[i,#,#],{i,4,10}],#]==0&] (* _Harvey P. Dale_, Nov 07 2017 *)
%K nonn
%O 1,2
%A _Robert G. Wilson v_, Sep 22 2000
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