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Michi’s blog » archive for November, 2011

 A quick python hack for a mathematical puzzle

  • November 12th, 2011
  • 4:09 pm

So, today I saw this in my Twitter feed:

«Phil Harvey wants us to partition {1,…,16} into two sets of equal size so each subset has the same sum, sum of squares and sum of cubes.» — posted by @MathsJam and retweeted @haggismaths.

Sounds implausible was my first though. My second thought was that there aren’t actually ALL that many of those: we can actually test this.

So, here’s a short collection of python lines to _do_ that testing.

import itertools
allIdx = range(1,17)
sets = itertools.combinations(allIdx,8)
setpairs = [(list(s), [i for i in allIdx if i not in s]) for s in sets]
def f((s1,s2)): return (sum(s1)-sum(s2), sum(map(lambda n: n**2, s1))-sum(map(lambda n: n**2, s2)), sum(map(lambda n: n**3, s1))-sum(map(lambda n: n**3, s2)))

goodsets = [ss for ss in setpairs if f(ss) == (0,0,0)]

And back comes one single response (actually, two, because the comparison is symmetric).