login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A190359 Largest prime factor of the least number having exactly two odd prime factors that differ by 2^n. 0
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 (list; graph; refs; listen; history; text; internal format)
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: A159080 A227770 A038881 * A045441 A128841 A057733

Adjacent sequences:  A190356 A190357 A190358 * A190360 A190361 A190362

KEYWORD

nonn

AUTHOR

Michel Lagneau, May 09 2011

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 20 17:40 EDT 2019. Contains 328268 sequences. (Running on oeis4.)