A056750 - OEIS

A056750

Numbers n such that n | 7^n + 6^n + 5^n + 4^n + 3^n + 2^n + 1^n.

1, 2, 4, 7, 10, 14, 28, 49, 50, 70, 98, 196, 209, 250, 343, 350, 490, 539, 668, 686, 1250, 1309, 1372, 1519, 1750, 1919, 2401, 2450, 2690, 2849, 3430, 4450, 4802, 6250, 8750, 9212, 9590, 9604, 9982, 10717, 12250, 15698, 16807, 17150, 18790, 24010, 31250

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..47.

MATHEMATICA

Do[ If[ Mod[ PowerMod[ 7, n, n ] + PowerMod[ 6, n, n ] + PowerMod[ 5, n, n ] + PowerMod[ 4, n, n ] + PowerMod[ 3, n, n ] + PowerMod[ 2, n, n ] + 1, n ] == 0, Print[ n ] ], {n, 1, 10^6} ]

Select[Range[31500], Divisible[Plus@@(Range[7]^#), #]&] (* or *) Select[ Range[ 31500], Mod[Total[PowerMod[Range[7], #, #]], #]==0&] (* The second program is much faster than the first, and the second program is only a rewrite of the first program above *) (* Harvey P. Dale, Mar 12 2018 *)

CROSSREFS

Cf. A001554.

Sequence in context: A170890 A079963 A261252 * A171926 A171930 A276164

Adjacent sequences: A056747 A056748 A056749 * A056751 A056752 A056753

KEYWORD

nonn

AUTHOR

Robert G. Wilson v, Aug 25 2000

STATUS

approved