[seqfan] Dual Brier problem

[Tomasz Ordowski]

Dear SeqFans!

Let's define:

Odd numbers k such that k2^n+-1 are both composite
and k+-2^n are both composite for all 2^n < k.

Are there such numbers k < 3316923598096294713661 ?
Cf. https://oeis.org/A076335 (the smallest Brier number).

https://en.wikipedia.org/wiki/Sierpinski_number#Dual_Sierpinski_problem

https://en.wikipedia.org/wiki/Riesel_number#The_dual_Riesel_problem

Best regards,

Thomas