*** Combinations of 4 items in a group of 10
There are 210 (red tile position 10 - 4) different combinations (when the order does not matter) of 4 items in a group of 10.
There are 715 (green tile) different combinations with repetitions of 4 items in group of 10.
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This is called combination (or k-combination) in mathematic, id est no matter of the order of the elements and no repetition of elements.
The formula is the binomial coefiicent one.
n!
C(n,k) = ----------
k!(n-k)!
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perl -E "say @$_ for grep{$$_[0]!=$$_[1] and $$_[0]!=$$_[2] and $$_[0]!=$$_[3] and $$_[1]!=$$_[2]
and $$_[1]!=$$_[3] and $$_[2]!=$$_[3]} map { [split '',sprintf '%04s',$_]} 0..9999;"