[Jprogramming] Unforgettable times

[Roger Hui]

Because "interesting" is undefined and open-ended,
this "mission" is not that difficult.  The following is
one way to solve it:

a. Go to Sloane's indispensable On-Line Encyclopaedia
of Integer Sequences.
http://www.research.att.com/~njas/sequences/

b. Enter the number n in the search box.

c. You will get quite a few sequences containing n.
Find an intersection in which n is the smallest element.

For example, n=391.  There are 922 hits.  Consider the 
hits in order:

 - A078972 a semiprime whose prime factors have an equal 
number of decimal digits. 

- A078972 number of permutations satisfying i-2<=p(i)<=i+4 

Already the intersection is just 6, 391,...

- A133630 nonprime number k such that binomial(k+p,k) mod k=1
where p=1.  6 is not an element of this sequence (but 391 is).  
We have an an "interesting fact" about 391.



----- Original Message -----
From: Dan Bron <j at bron.us>
Date: Saturday, August 22, 2009 18:37
Subject: Re: [Jprogramming] Unforgettable times
To: 'Programming forum' <programming at jsoftware.com>

> I wrote:
> > http://www2.stetson.edu/~efriedma/numbers.html  .  
> But 226 
> > has lost its title.
> 
> This page lists an interesting fact about each first 10,000 non-
> negative numbers.   So far, it can't find an 
> interesting fact
> about any of these numbers:
> 
> 	391 424 460 508 514 534 549 557 611 622
> 	647 655 674 685 698 702 706 723 725 754
> 	758 759 761 772 774 776 779 790 796 807
> 	811 817 824 826 828 830 837 838 845 860
> 	865 871 886 890 893 908 915 921 928 931
> 	932 937 938 944 947 954 962 965 970 971
> 	978 980
> 
> So 391 now holds the title as the smallest uninteresting 
> number.  Your mission, should you choose to accept it, is 
> to find a
> reason 391 is interesting.  Then 424.  Then 460.  Etc.