[https://www.weheartswift.com/higher-order-functions-map-filter-reduce-and-more/](url)

rowSumOddNumbers_stride.reduce

/* Given the triangle of consecutive odd numbers:

             1
          3     5
       7     9    11
   13    15    17    19
21    23    25    27    29
...
Calculate the row sums of this triangle from the row index (starting at index 1) e.g.:

rowSumOddNumbers(1) // 1
rowSumOddNumbers(2) // 3 + 5 = 8

*/

func rowSumOddNumbers(_ row: Int) -> Int {
    var x = 1 + (row - 1) * row
    var y = x + (row - 1) * 2 + 1
    return stride(from: x, to: y, by: 2).reduce(0, +)
}