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Least number having exactly two odd prime factors that differ by 2^n.
2

%I #10 Apr 06 2018 03:47:29

%S 15,21,33,57,185,201,393,1841,5753,7217,10265,12297,139553,607577,

%T 98313,196617,3801929,786441,27790073,7340081,35651873,281022857,

%U 92274809,721422137,1375733393,6509569217,3892314953,805306377

%N Least number having exactly two odd prime factors that differ by 2^n.

%H G. C. Greubel, <a href="/A190358/b190358.txt">Table of n, a(n) for n = 1..1000</a>

%e a(5) = 185 because 185 = 5 * 37 , and 37 - 5 = 32 = 2^5.

%t f[n_] := Block[{p = 3}, While[! PrimeQ[p] || ! PrimeQ[p + 2^n], p++]; p (p + 2^n)]; Table[f[n], {n, 1, 60}]

%Y Cf. A190052.

%K nonn

%O 1,1

%A _Michel Lagneau_, May 09 2011