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 1d comment 4-digit number, where $d_{1000} \lt d_{100} \lt d_{10}\lt d_{1}$ This StackExchange site is specifically about a software system called Mathematica. One solution to this problem with it is With[{digits = Array[c, 4]}, FromDigits[digits] /. Solve[Flatten@{Less@@digits, 1 <= # <= 9 & /@ digits}, digits, Integers]]. 2d reviewed Approve Loading FeynCalc Apr 24 awarded Good Answer Apr 24 comment How can I plot two concentric circles with a polygon inscribed in one and circumscribed about the other @J.M. I guess I wanted to write the solution starting from CirclePoints, and it didn't turn out too awkward to do so. The first sentence in my answer expresses the Weltschmerz involved in expressing the solution only in this manner. :) Apr 24 comment How can I plot two concentric circles with a polygon inscribed in one and circumscribed about the other @J.M. It was a strange experiment of the "avoid explicit trigonometry" sorts. :) Apr 24 comment Find the number of $n$ such that $n!$ is a sum of three squares I wasn't aware of PowersRepresentations, good to know! (Assuming one actually finds other applications than snarky Mma.SE answers for it...) Apr 24 revised How can I plot two concentric circles with a polygon inscribed in one and circumscribed about the other deleted 12 characters in body Apr 24 reviewed Leave Open Average function value over an Interval Apr 24 reviewed Close What is the good source to study advanced custom coding in Mathematica Apr 24 answered How can I plot two concentric circles with a polygon inscribed in one and circumscribed about the other Apr 24 reviewed No Action Needed How can I plot two concentric circles with a polygon inscribed in one and circumscribed about the other Apr 24 comment Find the number of $n$ such that $n!$ is a sum of three squares Make your search space bounded: Solve[{n! == x^2 + y^2 + z^2, x <= y <= z, Sequence @@ (0 < # < 70 & /@ {x, y, z})}, {x, y, z, n}, Integers] (* {{x -> 1, y -> 1, z -> 2, n -> 3}, {x -> 2, y -> 2, z -> 4, n -> 4}, {x -> 2, y -> 4, z -> 10, n -> 5}, {x -> 4, y -> 20, z -> 68, n -> 7}, {x -> 8, y -> 16, z -> 20, n -> 6}, {x -> 12, y -> 36, z -> 60, n -> 7}, {x -> 20, y -> 44, z -> 52, n -> 7}} *) - this is not necessarily fast, but it works. Apr 24 comment Writing a word with straight lines @VividD Actually I haven't come up with anything specifically fancy myself, but reg can be substituted with any geometric region (although mesh region is probably required for performance). Tweaking of distribution of properties of candidate lines and adding an exponent to weight values are two additional variations which come to my mind... Apr 23 comment Writing a word with straight lines @MartinBüttner Yes... I think line-mesh intersection should really work even otherwise and one should be just be able to check out RegionMeasure after that, but it appears that's a bit optimistic. I didn't actually notice you mentioned this problem on your answer, but played with it on my own... Apr 23 awarded Nice Answer Apr 23 revised Writing a word with straight lines deleted 5 characters in body Apr 23 answered Writing a word with straight lines Apr 19 comment DiscretizeRegion fails for a triangular region Could you report this as a bug to Wolfram Research and add information on the case number they give to it? Apr 19 revised DiscretizeRegion fails for a triangular region edited tags Apr 19 comment Is there research about the Mathematica programming paradigm? @LeonidShifrin Multiple independent compilers (or interpreters, if the language is particularly dynamic) show even better rigour. For instance, Python technically has a language spec, but you can't really replicate the language by just reading and understanding it. PyPy authors had to basically reverse-engineer CPython functionality in order to provide an another indistinguishable enough implementation. They at least had the source code; in the case of WL, the source code is considered a trade secret...