Page **1** of **1**

### Problem 672

Posted: **Tue May 28, 2019 12:35 pm**

by **jaap**

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**

by **hk**

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**

by **jaap**

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**

by **macgupta**

I agree with jaap. H is poorly defined.