j #~ (j e. <:p: j) * (j e. >:*:j) * (2...@q: j) * 2...@q:@(|.&.":"0) j=: 1+i.1e6 226 47962 95482 103042 140626 194482 370882
----- Original Message ----- From: Roger Hui <[email protected]> Date: Saturday, August 22, 2009 14:29 Subject: Re: [Jprogramming] Unforgettable times To: Programming forum <[email protected]> > 226: the first emirprime which is the successor of > a perfect square and the precedessor of a prime. > > http://mathworld.wolfram.com/Emirpimes.html > > > > ----- Original Message ----- > From: Randy MacDonald <[email protected]> > Date: Saturday, August 22, 2009 13:42 > Subject: Re: [Jprogramming] Unforgettable times > To: Programming forum <[email protected]> > > > What is memorable about 226? > > > > Roger Hui wrote: > > > 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
