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A336773 a(n) is the least prime of the form 2^j*3^k + 1, j > 0, k > 0, j + k = n. a(n) = 0 if no such prime exists. 5
7, 13, 37, 73, 97, 193, 577, 769, 3457, 10369, 0, 12289, 629857, 839809, 147457, 995329, 1990657, 786433, 5308417, 120932353, 14155777, 28311553, 0, 113246209, 29386561537, 3439853569, 6879707137, 1811939329, 18345885697, 3221225473, 1253826625537, 0, 85691213438977 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Robert Israel, Table of n, a(n) for n = 2..2193

MAPLE

f:= proc(n) local k, p;

   for k from 1 to n-1 do

     p:= 2^(n-k)*3^k+1;

     if isprime(p) then return p fi

   od;

   0

end proc:

map(f, [$2..40]); # Robert Israel, Aug 30 2020

PROG

(PARI) for(n=2, 34, my(pm=oo); for(j=1, n-1, my(k=n-j, p=2^j*3^k+1); if(isprime(p), pm=min(p, pm))); print1(if(pm==oo, 0, pm), ", "))

CROSSREFS

Cf. A033845, A058383, A336772 (positions of 0).

Sequence in context: A088985 A022005 A281317 * A118819 A118525 A213537

Adjacent sequences:  A336770 A336771 A336772 * A336774 A336775 A336776

KEYWORD

nonn

AUTHOR

Hugo Pfoertner, Aug 28 2020

STATUS

approved

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Last modified October 23 14:42 EDT 2021. Contains 348214 sequences. (Running on oeis4.)