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### Problem 672

Posted: Tue May 28, 2019 12:35 pm
Is "no nothing" a typo for "do nothing"?

Shouldn't there be a floor function around the $\frac{7^K-1}{11}$ term? I don't think there is a universally accepted meaning for a sum where the upper limit for the index variable is not an integer.

### Re: Problem 672

Posted: Tue May 28, 2019 12:56 pm
jaap wrote: Tue May 28, 2019 12:35 pm Is "no nothing" a typo for "do nothing"?
Yes. Corrected.
Shouldn't there be a floor function around the $\frac{7^K-1}{11}$ term? I don't think there is a universally accepted meaning for a sum where the upper limit for the index variable is not an integer.
Please investigate if $\frac{7^K-1}{11}$ isn't an integer for the values of K used in the problem.

### Re: Problem 672

Posted: Tue May 28, 2019 1:44 pm
Thanks for fixing that hk.
hk wrote: Tue May 28, 2019 12:56 pm
jaap wrote: Tue May 28, 2019 12:35 pm Shouldn't there be a floor function around the $\frac{7^K-1}{11}$ term? I don't think there is a universally accepted meaning for a sum where the upper limit for the index variable is not an integer.
Please investigate if $\frac{7^K-1}{11}$ isn't an integer for the values of K used in the problem.
Fair enough I suppose. Still, it irks me that a definition of H(K) is given as if it holds for any K. I fully accept that you have to assume K is an integer, since this is in the context of an integer problem, but for me it feels like a step too far that it has the unstated assumption that the definition only makes sense for specific integer values of K and is therefore defined only for those values. I appreciate that this may be a minority opinion, and it's no big deal really.
Anyway, I'll move on to trying to solve the problem.

### Re: Problem 672

Posted: Thu Dec 12, 2019 4:40 am
I agree with jaap. H is poorly defined.