Non Adjacent Cells In Array

This is acceptable

Code:

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=COVAR(A1:D1,E1:H1)

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And so is this

Code:

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=COVAR({3,2,4,5,6}, {9,7,12,15,17})

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However, this isn't

Code:

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=COVAR({A1,C1,E1,G1}, {B1,D1,F1,H1})

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Any idea why?
Is it possible to have non adjacent cells in an array?