[seqfan] Re: 2225

[M. F. Hasler]

On Wed, May 29, 2019, 07:33 Tomasz Ordowski <tomaszordowski at gmail.com>
wrote:

> What is the smallest odd number that,
> preceded by any number of 1's in base 2, gives only composite numbers?
>


I don't think that such a number exists, but one could certainly add the
sequence
of the least a(n) such that appending 0,1,2,...,n binary 1's in front
(and/or, maybe, adding sum_{k≤m} 2^k with 0 ≤ m ≤ n)
yields only composite numbers.

--
Maximilian

I also ask for the smallest prime of this property.
>