The problem is that _every_ number has something
notable about it, so that each number is "unforgettable"
and consequently it's hard to remember any single
one of them.
0000 all zeros
0001 first counting number
0002 first prime number
0003 first odd prime
0004 first composite number
...
24 60 #: ?. */ 24 60
1 6
0106 first number greater than 100 with 2 prime factors
etc.
You have most likely heard of the story about Hardy
and Ramanujan. One day Hardy took a taxi to visit
Ramanujan. On arriving Hardy told Ramanujan that
the taxi had the 4-digit number n on its license plate,
a thoroughly unremarkable number. Ramanujan
immediately remarked that n is the first number that ... .
I forget what n or the property was, something like,
n is the first number that can be written as the sum
of two perfect cubes in two different ways, something
typically Ramanujanish.
Yes, that was it:
c=: i*i*i=: >:i.200
t=: (</~i.200) * +/~c
d=: </.~ ,t
(2=#&>d)#d
+---------+---------------+---------------+---------+--
|1729 1729|1092728 1092728|3375001 3375001|4104 4104| ...
+---------+---------------+---------------+---------+--
<./ {.&> (2=#&>d)#d
1729
I. , 1729 = t
11 1609
1 + (#t) #: 11 1609
1 12
9 10
+/ 1 12 ^ 3
1729
+/ 9 10 ^ 3
1729
Now that I have worked out the number I can find the
story on the net: http://en.wikipedia.org/wiki/1729_(number)
p.s. In my youth, when I needed to remember a (5-digit)
number for a time, I would try to compute its largest
prime factor by mental calculation. Try it and you'll
see why that works.
----- Original Message -----
From: Kip Murray <[email protected]>
Date: Saturday, August 22, 2009 5:27
Subject: Re: [Jprogramming] Unforgettable times
To: Programming forum <[email protected]>
> To narrow the puzzle,
>
> times 3 4 5 NB. Unforgettable
> 1 6 2 0
> 1 8 1 2
> 1 2 0 7
> timedata i. 1 8 1 2
> 4
> times i.8
> 1 2 3 4
> 1 4 1 4
> 1 4 2 8
> 1 6 2 0
> 1 8 1 2
> 1 2 0 7
> 1 2 3 4
> 1 4 1 4
>
> You are encouraged to choose your own unforgettable times seen
> on a 24-hour
> digital clock.
>
>
> Kip Murray wrote:
> > Who could forget
> >
> > times 3 4 5
> > 1 6 2 0
> > 1 8 1 2
> > 1 2 0 7
> >
> > ?
> >
> > Kip Murray wrote:
> >> Write a verb that produces unforgettable times on a 24-hour
> digital clock: who
> >> could forget an appointment at 12:34 or 14:14 or 14:28
> ? It's too bad that
> >> 31:41 , 27:18 and 69:31 do not fit on the clock.
> >>
> >> times 0
> >> 1 2 3 4
> >> times 0 1
> >> 1 2 3 4
> >> 1 4 1 4
> >> times i. 5
> >> 1 2 3 4
> >> 1 4 1 4
> >> 1 4 2 8
> >> 1 2 3 4
> >> 1 4 1 4
> >> NB. Oh, well, you will do
> better than this
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