2!>:21
On Aug 29, 2017 10:17, "Murray Eisenberg" <[email protected]> wrote: > The sum in question is twice the sum of the integers from 1 to 21. By the > well-known formula (sometimes attributed to Gauss), the latter sum is half > the product of 21 and 21 + 1, so the sum in question is > > */21+i. 2 > 462 > > > > On28 Aug 2017 12:02:57 -0500,S kip Cave <[email protected] > <mailto:[email protected]>> wrote: > > > > A simple problem posted on Quora: > > > > What is the sum of all the even numbers from 2 to 42? > > > > My J solution: > > a=:>:i.42 > > +/(-.2|a)#a > > 462 > > > > I'm sure this can be done in a single line using a hook or fork. > > but I'm not clear enough with the train rules to put this all together > > on a single line. > > Any suggestions? > > —— > Murray Eisenberg [email protected] > Mathematics & Statistics Dept. > Lederle Graduate Research Tower phone 240 246-7240 (H) > University of Massachusetts > 710 North Pleasant Street > Amherst, MA 01003-9305 > > > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
