A123359 - OEIS

%I #7 Oct 25 2017 23:32:53

%S 0,1,1,1,1,3,2,4,1,2,1,6,4,3,1,1,11,6,7,21,3,8,2,5,1,7,1,4,12,11,2,4,

%T 7,10,15,6,1,30,3,8,11,11,2,6,3,16,14,17,17,4,18,50,36,6,71,6,29,2,11,

%U 6,4,16,18,1,8,6,17,9,15,14,54,12,17,12,41,4,29,3,7,25,11,35,23,24,31,27,18

%N Least m such that 3^n+2^m is prime.

%H G. C. Greubel, <a href="/A123359/b123359.txt">Table of n, a(n) for n = 0..1000</a>

%e a(0)=0 because 3^0+2^0=1+1=2 is prime,

%e a(5)=3 because 3^5+2^3=243+8=251 is prime.

%t lm[n_]:=Module[{c=3^n,m=0},While[!PrimeQ[c+2^m],m++];m]; Array[lm,90,0] (* _Harvey P. Dale_, May 01 2013 *)

%Y Cf. A123340 = least m such that 2^n+3^m is prime, A123342 = least m such that 2^n+5^m is prime.

%K nonn

%O 0,6

%A _Zak Seidov_, Oct 12 2006