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50 - or more (Posted on 2020-09-10) Difficulty: 4 of 5
Let's start with a triplet of integers, say (1, 2, 5) and a set of mathematical operations (+, -, *, /, ^, sqrt, fact!, concatenation, brackets).

Our task will be to represent all (or almost all - as explained below) integers from 1 to n using some or all of the initial triplet and any quantity of operations defined above.

So:
1=1
6=1+5
9=5*2-1
13=15-2
27=51-4!
60=12*5 etc

Let's define n as the first occurrence of not being able to find a valid representation for n+1 and for n+2. I believe that in our case n=17 (15+2), since neither 18 nor 19 get valid solutions.

You are requested to find a triplet of integers (a,b,c) enabling a maximal n.

No Solution Yet Submitted by Ady TZIDON    
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re(3): some hints & remarks @ Ch | Comment 9 of 14 |
(In reply to re(2): some hints & remarks @ Ch by Ady TZIDON)

I agree with Dej Mar, there were only 9 mathematical operations. If factorials are a family, why not roots as well? And square brackets could be a family that includes floor or ceiling (especially floor, as in many instances it's understood that the square brackets signify floor without even leaving out the top horizontal bar).


BTW, my first post's result was based on 4, 7 and 9 because the bug caused stopping at the first total number of failures exceeding 2. I first fixed that bug and redid 4, 7, 9. Later I ran the full set of combinations to come out with 4, 9 and 9.  This latter has a lot of holes but the first two in a row come later.

  Posted by Charlie on 2020-09-11 07:38:31
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