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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.
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%I #9 Aug 30 2020 22:15:56

%S 7,13,37,73,97,193,577,769,3457,10369,0,12289,629857,839809,147457,

%T 995329,1990657,786433,5308417,120932353,14155777,28311553,0,

%U 113246209,29386561537,3439853569,6879707137,1811939329,18345885697,3221225473,1253826625537,0,85691213438977

%N 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.

%H Robert Israel, <a href="/A336773/b336773.txt">Table of n, a(n) for n = 2..2193</a>

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

%p for k from 1 to n-1 do

%p p:= 2^(n-k)*3^k+1;

%p if isprime(p) then return p fi

%p od;

%p 0

%p end proc:

%p map(f, [$2..40]); # _Robert Israel_, Aug 30 2020

%o (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),", "))

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

%K nonn

%O 2,1

%A _Hugo Pfoertner_, Aug 28 2020