A057266 - OEIS

%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