"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."
Three words spring to mind. Pen. Paper. Pocket. :-)). 2009/8/22 Roger Hui <[email protected]>: > 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 > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
