1,1

The least number having exactly two odd prime factors that differ by 2^n is given by the sequence A190358.

Table of n, a(n) for n=1..28.

a(5) = 37 because A190358(5) = 185 = 5 * 37 , and 37 is the largest prime divisor

such that 37 - 5 = 32 = 2^5.

with(numtheory):for m from 1 to 30 do: k:=2^m:id:=0:for n from 1 to 900000000

while(id=0) do: x:=factorset(n):n1:=nops(x):n2:=bigomega(n):if n1=2 and n2=2

and x[2]=x[1]+k then id:=1:printf(`%d, `, x[2]):else fi:od:od:

Cf. A190358.

Sequence in context: A159080 A227770 A038881 * A045441 A128841 A057733

Adjacent sequences: A190356 A190357 A190358 * A190360 A190361 A190362

nonn

Michel Lagneau, May 09 2011

approved