1,1

The first four terms are A065341(1), A065341(2), A065341(7), A065341(9) and have the form 2^m-1. Are there terms not of this form?

Composite 2^n-1 belong to this sequence when n is in A005385 (e.g., 2^83-1, 2^167-1, etc.)

No other terms below 2^64. - Max Alekseyev, May 28 2014

Table of n, a(n) for n=1..4.

2047=6*341+1; 2^2046 == 1 (mod 2047); 2^340 == 1 (mod 341).

Subsequence of A001567.

Sequence in context: A131952 A065341 A135976 * A289476 A222526 A035892

Adjacent sequences: A236370 A236371 A236372 * A236374 A236375 A236376

nonn,more

Alzhekeyev Ascar M, Jan 24 2014

a(4) from Max Alekseyev, May 28 2014

approved