Problem 221

timpa · Post by **timpa** » Mon Feb 02, 2009 2:36 pm

Can someone confirm the following Alexandrian numbers?

1000th: 787167192
10000th: 649280243274
100000th: 584788819726944

Georg · Post by **Georg** » Mon Feb 02, 2009 6:44 pm

No, I got a different result.

estanford · Post by **estanford** » Sat Jan 09, 2010 2:14 pm

There may be some bugs in my code, but I get 772168278 as the thousandth Alexandrian.

EDIT: I know my algorithm successfully generates all Alexandrians up to the fortieth in sequence, but I can't verify it beyond that.

zwuupeape · Post by **zwuupeape** » Sat Jan 09, 2010 3:55 pm

This is correct. The 1000th Alexandrian Integer is indeed 772168278.

Believe it or not, but if you solve the problem, you'll see that there's an algorithm that finds these numbers O(nlogn) time.

Oliver1978 · Post by **Oliver1978** » Wed Mar 25, 2015 10:49 pm

For the 10,000th I get 628[...]090 and for the 100,000th I get 232[...]8200.

???

Svartskägg · Post by **Svartskägg** » Thu Mar 26, 2015 1:40 pm

leghorn wrote:For the 10,000th I get 628[...]090 and for the 100,000th I get 232[...]8200.

The value for 10000 is right, the other one wrong.

Oliver1978 · Post by **Oliver1978** » Thu Mar 26, 2015 2:56 pm

Oh well, I suspect there's an overflow.

h_anand · Post by **h_anand** » Wed May 27, 2015 1:50 am

Svartskägg wrote:
leghorn wrote:For the 10,000th I get 628[...]090 and for the 100,000th I get 232[...]8200.
The value for 10000 is right, the other one wrong.

I get the following values:

Thousandth: 772...278
Ten thousandth: 628...090
Hundred thousandth: 756...504

Is the value for Hundred thousandth correct?

Is overflow possible? I mean, would I encounter values larger than 2 ^ 64?

thank you,

Svartskägg · Post by **Svartskägg** » Wed May 27, 2015 6:05 pm

h_anand wrote:Hundred thousandth: 756...504
Is the value for Hundred thousandth correct?

No

h_anand wrote:Is overflow possible? I mean, would I encounter values larger than 2 ^ 64?

I don't remember how my program works, but it uses no variable with more than 64 bits and it gives the right answer, so presumably there is no overflow.

h_anand · Post by **h_anand** » Thu Jun 18, 2015 7:11 pm

Thank you, Svartskägg. I was able to solve the problem eventually. To give you an idea of my level, this is the toughest problem I have solved till date. My attempt at solving the arithmetic derivative might take several years to complete.

Oliver1978 · Post by **Oliver1978** » Thu Aug 06, 2015 6:26 pm

I've iterated my way into this, but I've encountered an issue, which keeps me wondering. My code is ready to run, and it does find the correct answer...but not in the right spot. Would somebody care to take a look?

edit

Top of the evening. Solved this one. Had an overflow, temporary big integer helped me out.

pxor · Post by **pxor** » Sun Mar 17, 2019 8:23 pm

Hey, could anyone confirm these numbers are correct ?, thanks.

20k - 488-------508
60k - 124---------660
100k - 148----------350
140k - 276-----------940

hk · Post by hk » Sun Mar 17, 2019 8:36 pm

The first two are correct. The second two not.

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