New answers tagged graph-theory
5
Not being a follower of this particular YouTube channel, this is new to me. However, it strongly reminds me of another puzzle seen on Puzzling earlier this year, which I believe has a similar mechanism at heart... In which case, the answer is that:
2
Freddy Barrera, using SAGE, has determined all integers not greater than 1000 whose divisibility graph is non-planar:
32, 36, 48, 60, 64, 72, 80, 84, 90, 96, 100, 108, 112, 120, 126, 128, 132, 140, 144, 150, 156, 160, 162, 168, 176, 180, 192, 196, 198, 200, 204, 208, 210, 216, 220, 224, 225, 228, 234, 240, 243, 252, 256, 260, 264, 270, 272, 276, 280, 288, ...
answered Nov 21 at 16:46
Bernardo Recamán Santos
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6
A graph is non-planar
Therefore, the smallest positive integer with a non-planar proper divisor graph is
Finding the first two consecutive integers with this property is more complicated, because
It turns out that
Thus, the two smallest consecutive numbers whose proper divisors form a non-planar graph are
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