Rosettacode has a task now, for this item. http://rosettacode.org/wiki/Prime_conspiracy#J
And, hypothetically speaking, it should be straightforward to do the extra credit problem. But that doesn't work. Given: dgpairs=: 2 (,'->',])&":/\ 10 | p: combine=: ~.@[ ,.~ ' ',.~ ":@,.@(+//.) We can try this: /:~ combine&;/|: (~.;#/.~)@dgpairs@((+ i.)/)"1 (1e6*i.1e3),.1e6+999>i.1e3 |limit error: dgpairs ... but p: doesn't work for values like 1e9 (1 p: works, but not p: itself). And, for example, Roger has worked out some ways of dealing with large primes -- see looking at http://code.jsoftware.com/wiki/Essays/Primality_Tests -- but we don't have anything that's a drop in replacement for the p: monad. So this presents something of a problem - how would we tackle a problem like this? (Please feel free to change forum to programming if you've got working code rather than just ideas...). Thanks, -- Raul On Tue, Mar 15, 2016 at 7:02 AM, Cliff Reiter <[email protected]> wrote: > A look at the frequencies of pairs of last digits of successive primes: > /:~({.,#)/.~2]\10|p:4+i.1e7 > > 1 1 446808 > > 1 3 756071 > > 1 7 769924 > > 1 9 526953 > > 3 1 593196 > > 3 3 422302 > > 3 7 714795 > > 3 9 769915 > > 7 1 639383 > > 7 3 681759 > > 7 7 422289 > > 7 9 756852 > > 9 1 820369 > > 9 3 640076 > > 9 7 593275 > > 9 9 446032 > > The 1 follows 1 as rare as 9 follows 9, but rarer is 3 follows 3 as rare > as 7 follows 7. 9 1 most popular! Very curious. Probably should move to > JProg' Best, Cliff > > > > > On 3/14/2016 12:03 PM, R.E. Boss wrote: > >> >> https://www.quantamagazine.org/20160313-mathematicians-discover-prime-conspiracy/ >> R.E. Boss >> ---------------------------------------------------------------------- For >> information about J forums see http://www.jsoftware.com/forums.htm >> > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
