20200127, 07:31  #1 
Mar 2018
20F_{16} Posts 
primes of ther form 19*3*2^k+ or 1
I found only three primes of this form up to k=10.000. (k=2,8,18)
Are they finite? 
20200127, 07:56  #2 
Aug 2006
1754_{16} Posts 
There should be infinitely many. You can look at the residue classes and do an infinite product to guess how sparse they will be.

20200127, 13:59  #3  
Feb 2017
Nowhere
29×149 Posts 
Looks like the OP missed quite a few. If the intent was to find exponents on both lists, the exponent 10 is missing and the exponent 18 is wrong.
From the List of primes k*2^{n} + 1 for k < 300 we have for k = 19*3 = 57, Quote:
From the List of primes k*2^{n}  1 for k < 300, again for k = 19*3 = 57, Quote:
Last fiddled with by Dr Sardonicus on 20200127 at 14:24 Reason: w, misread multiplier, had to redo. 

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