A190148 Largest prime factor of the least number having exactly two odd prime factors that differ by 2*n^2.

5, 11, 23, 37, 53, 79, 101, 131, 167, 211, 271, 293, 349, 397, 457, 523, 601, 653, 727, 811, 887, 971, 1061, 1163, 1279, 1381, 1471, 1571, 1693, 1811, 1933, 2053, 2207, 2341, 2467, 2609, 2741, 2917, 3049, 3203, 3373, 3533, 3701, 3877, 4057, 4243, 4421, 4621, 4813, 5003, 5209

Offset

1,1

Comments

The least number having exactly two odd prime factors that differ by 2*n^2 is given by the sequence A190052 .

Links

Table of n, a(n) for n=1..51.

Example

a(11) = 271 because A190052(11) = 7859 =29 * 271 , and 271 is the largest prime
  divisor such that 271 - 29 = 242 = 2*11^2.

Maple

with(numtheory):for m from 1 to 60 do: k:=2*m^2:id:=0:for n from 1 to 100000
  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. A190052.

Sequence in context: A235386 A061769 A169744 * A281875 A143125 A147081

Adjacent sequences: A190145 A190146 A190147 * A190149 A190150 A190151

Keyword

nonn,easy

Author

Michel Lagneau, May 05 2011

Status

approved