A190663 Largest prime factor of the least semiprime whose prime factors differ by 2*n!

5, 7, 17, 53, 251, 1447, 10091, 80651, 725789, 7257629, 79833613, 958003271, 12454041629, 174356582419, 2615348736019, 41845579776037, 711374856192023, 12804747411456023

Offset

1,1

Links

Table of n, a(n) for n=1..18.

Example

a(5) = 251 because A190662(5) = 2761 = 11 * 251 , and 251 is the largest prime
  divisor such that 251 - 11 = 240 = 2*120 = 2*5!

Maple

with(numtheory):for m from 1 to 18 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 %d \n", m, x[2]):else fi:od:od:

Crossrefs

Cf. A190662.

Sequence in context: A248085 A079604 A101580 * A123195 A248480 A243844

Adjacent sequences: A190660 A190661 A190662 * A190664 A190665 A190666

Keyword

nonn

Author

Michel Lagneau, May 16 2011

Status

approved