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Advent calendar 2018
18 December
All 2018 advent puzzles
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There are 6 terms in the expansion of \((x+y+z)^2\):
$$(x+y+z)^2=x^2+y^2+z^2+2xy+2yz+2xz$$
Today's number is number of terms in the expansion of \((x+y+z)^{16}\).
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153
In general, the expansion of \((x+y+z)^n\) will have \(\frac12n(n-1)\) terms.
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sum to infinity
ave
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coins
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cryptic crossnumbers
symmetry
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consecutive integers
algebra
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regular shapes
star numbers
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sequences
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factors
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range
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taxicab geometry
spheres
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christmas
numbers
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geometric mean
irreducible numbers
lists
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pentagons
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division
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