cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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

Original entry on oeis.org

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

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Comments

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

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