

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
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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



