A319245 Numbers k such that k^2 + 1 divides 2^k + 8.

0, 1, 17, 37, 77, 197, 513, 993, 1837, 2617, 2637, 4097, 5437, 65537, 261633, 364137, 437837, 2097153, 16777217, 32761917, 54644032237, 68719476737, 137438953473, 1099511627777

Offset: 1

Author

Altug Alkan, Sep 15 2018

Keywords

• nonn
• more

Comments

Prime terms are 17, 37, 197, 2617, 5437, 65537, 437837, ...

Numbers t such that 2^t + 1 is a term are 4, 9, 12, 16, 21, 24, 36, 37, 40, 45, 49, 52, 57, 64, 69, 76, 84, 96, ...

Crossrefs

Cf. A247220, A319216, A319233.

Programs

Mathematica

Select[Range[0, 9999], Divisible[2^# + 8, #^2 + 1] &] (* Alonso del Arte, Sep 16 2018 *)

PARI

isok(n)=Mod(2, n^2+1)^n==-8;

Extensions

a(21)-a(24) from Hiroaki Yamanouchi, Sep 16 2018