Consecutive Squarefrees, Not Coprime
Jud McCranie
j.mccranie at adelphia.net
Thu Aug 25 03:09:51 CEST 2005
Leroy Quet proposed this. David Wilson replied:
>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.
Don Reble said:
"Continuing my speculation on David's intentions and methods, the
sequence
11 (2) 5 29 31 (6) 23 7 17 (2) 19
yields a(6) <= 57879439071222. (Yay, the endpoints are squarefree.) "
----------
I've found that with high probability, a(6) = 9216772051242 (and its
partner is 9216772051254). At this point I can't be sure that there isn't
a smaller one, but there probably isn't a smaller one. Soon I hope to have
either a proof that it is the smallest (very likely it is) or possibly find
a smaller one.
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