24
The number 24 is equal to 
(four factorial).
A number puzzle asks to construct 24 in as many ways possible using elementary mathematical operations on three copies of the same digit. Example solutions include
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(1)
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(2)
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(3)
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(4)
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(5)
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(6)
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(7)
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(8)
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(9)
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where the not necessarily elementary "operation" of digit concatenation has been indicated using the symbol 
,
any solution with 2 can be replaced with the trivial substitution 
, and all occurrences
of 
and 
can be replaced
by 
, 
, 
, 
, etc.
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10 by 10 addition table
