Howell, Leonard W. (MSFC-VP62) wrote: > I'm at a Mathematica workshop and the class was given this challenge > problem: > > Find integers a,b,c,d such that a^3 + b^3 + c^3 +d^3 =31 > > and in general, write a program to give the solutions to a^3 + b^3 + c^3 > +d^3 =k, k=1,..., 350. > > Of course, some will be the empty set. > > Anyone have an approach for this problem?
Partial spoiler ahead. s=:134476 117367 _159380 _2x +/ s^3 31 No, I did not really solve it. I did it the old-fashioned way: let someone else do it. The case where a, b, c, and d are positive is covered at http://www.alpertron.com.ar/FCUBES.HTM and looks as though it would be a nice Mathematica application. The general problem is difficult: expressing 39 as a sum of 3 cubes (which is the way I "solved" the problem) was done relatively recently. I believe Noam Elkies has some methods for this kind of problem. Best wishes, John ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
