A233415 Odd numbers k such that 2k-1 divides 2^k-1.

1, 763425, 10888425, 40068105, 142086921, 191345625, 462784725, 468545025, 552451809, 595018305, 683993905, 956917125, 1013987349, 1024992045, 1567781325, 1581567885, 3094868865, 3312888345, 4839991545, 4882263477, 5064476505, 5613455925, 7303900125

Offset: 1

Author

Charles R Greathouse IV, Dec 09 2013

Keywords

• nonn

Comments

These seem to be much rarer than the corresponding even numbers.

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..51

Crossrefs

Subsequence of A081856.

Numbers 2a(n)-1 form a subsequence of A187787.

Programs

PARI

is(n)=n%2 && Mod(2, 2*n-1)^n==1