A190359 Largest prime factor of the least number having exactly two odd prime factors that differ by 2^n.

5, 7, 11, 19, 37, 67, 131, 263, 523, 1031, 2053, 4099, 8209, 16421, 32771, 65539, 131101, 262147, 524341, 1048583, 2097169, 4194371, 8388619, 16777259, 33554473, 67108961, 13417757, 268435459

Offset

1,1

Comments

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

Links

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

Example

a(5) = 37 because A190358(5) = 185 = 5 * 37 , and 37 is the largest prime divisor
  such that 37 - 5 = 32 = 2^5.

Maple

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:

Crossrefs

Cf. A190358.

Sequence in context: A349820 A227770 A038881 * A045441 A128841 A057733

Adjacent sequences: A190356 A190357 A190358 * A190360 A190361 A190362

Keyword

nonn

Author

Michel Lagneau, May 09 2011

Status

approved