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A240941 Numbers n such that n divides 2^n + 7. 3
1, 3, 15, 75, 6308237, 871506915, 2465425275, 2937864075, 2948967789, 83313712623, 195392257275, 11126651718075, 45237726869109, 2920008144904215 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Some larger terms: 213736983815110866141, 23423890178454972202084722709155. - Max Alekseyev, Sep 23 2016

LINKS

Table of n, a(n) for n=1..14.

OEIS Wiki, 2^n mod n

EXAMPLE

2^3 + 7 = 15 is divisible by 3. Thus 3 is a member of this sequence.

MATHEMATICA

k = 1; lst = {1, 3}; While[k < 2500000001, If[ PowerMod[2, k, k] + 7 == k, AppendTo[ lst, k]; Print[ k]]; k += 2]; lst (* Robert G. Wilson v, Aug 05 2014 *)

PROG

(PARI)

for(n=1, 10^9, if(Mod(2, n)^n==Mod(-7, n), print1(n, ", ")))

CROSSREFS

Cf. A033981.

Sequence in context: A294340 A059838 A079164 * A047015 A322186 A037759

Adjacent sequences:  A240938 A240939 A240940 * A240942 A240943 A240944

KEYWORD

nonn,more,hard

AUTHOR

Derek Orr, Aug 04 2014

EXTENSIONS

a(7)-a(9) from Robert G. Wilson v, Aug 05 2014

a(10)-a(14) from Max Alekseyev, Sep 23 2016

STATUS

approved

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Last modified June 12 16:18 EDT 2021. Contains 344959 sequences. (Running on oeis4.)