SUMPRODUCT(...)

Category: Math and trigonometry

Returns the sum of the products of corresponding array components

SUMPRODUCT(array1, [array2], [array3], ...)

Category: Statistical

Returns the k-th smallest value in a data set

SMALL(array, k)

Category: Lookup and reference

Returns the row number of a reference

ROW([reference])

Category: Lookup and reference

Returns a reference indicated by a text value

INDIRECT(ref_text, [a1])

-1

The formula first creates a number series till n-values and that is feed to small to get the n-smallest values, Then the values are summed by SUMPRODUCT function.