# [seqfan] Re: Nomination for 250000.

Neil Sloane njasloane at gmail.com
Sat Nov 15 12:51:03 CET 2014

```Dear Juri,
Please submit these two sequences to the OEIS,
and tell me the A-numbers:

"Numbers n such that n, 2^n - 1 and binomial coefficient(2^n - 1, n) are
all squarefree: 1, 2, 3, 11, 29, 31, 51, 55, 57, ... (finite)

Primes p such that 2^p - 1 is not squarefree: 359, 397, 419, ...
(infinite). "

By the way, the second one should have a cross-reference
saying "These are the primes in A049094."

Thank you

Best regards
Neil

Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Email: njasloane at gmail.com

On Fri, Nov 14, 2014 at 5:51 PM, юрий герасимов <2stepan at rambler.ru> wrote:

>
> Numbers n such that n, 2^n - 1 and binomial coefficient(2^n - 1, n) are
> all squarefree: 1, 2, 3, 11, 29, 31, 51, 55, 57, ... (finite)
> or Primes p such that 2^p - 1 is not squarefree: 359, 397, 419, ...
> (infinite). JSG.
```