A247205 Numbers k such that 2*k^2 - 1 divides 2^k - 1.

1, 18480, 8388480

Offset

1,2

Comments

a(4) > 2*10^10. - Chai Wah Wu, Dec 06 2014

Links

Table of n, a(n) for n=1..3.

Example

1 is in this sequence because 2*1^2 - 1 = 1 divides 2^1 - 1 = 1.

Prog

(Magma) [n: n in [1..100000] | Denominator((2^n-1)/(2*n^2-1)) eq 1];
(PARI) for(n=1, 10^9, if(Mod(2, 2*n^2-1)^n==+1, print1(n, ", "))); \\ Joerg Arndt, Nov 30 2014

Crossrefs

Cf. A247219, A247221.

Sequence in context: A209895 A190110 A157738 * A173274 A237012 A031817

Adjacent sequences: A247202 A247203 A247204 * A247206 A247207 A247208

Keyword

nonn,more,bref

Author

Juri-Stepan Gerasimov, Nov 30 2014

Extensions

a(3) from Joerg Arndt, Nov 30 2014

Status

approved