Consecutive Squarefrees, Not Coprime
David Wilson
davidwwilson at comcast.net
Sat Aug 20 23:00:07 CEST 2005
The gcd of any two consecutive squarefree numbers must be squarefree. Given
the k-tuple conjecture, I can show that every squarefree number is in fact
the gcd of two consecutive squarefrees (the k-tuple conjecture may not be
necessary here).
This leads us immediately to ask, for squarefree n, what is the smallest a
such that a and a+n are consecutive squarefrees with gcd(a, a+n) = n. I get
n a(n)
1 1
2 422
3 174
5 22830
6 <=1292013541080148674
7 234374
I'm sure my bound on a(6) is rather loose and could be tightened with a
little effort. It is not out of the question that the exact value could be
found.
a(10) seems hopeless.
a(11) would be about as hard as a(6).
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