A240941 Numbers k that divide 2^k + 7.

1, 3, 15, 75, 6308237, 871506915, 2465425275, 2937864075, 2948967789, 83313712623, 195392257275, 11126651718075, 45237726869109, 2920008144904215

Offset: 1

Author

Derek Orr, Aug 04 2014

Keywords

• nonn
• more
• hard

Comments

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

Examples

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

Links

• OEIS Wiki, 2^n mod n

Crossrefs

Cf. A033981, A168415.

Programs

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 *)

PARI

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

Extensions

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

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