1, 2, 19, 38
1, 2, 19, 38.
1, 2, 19, 38
The number of odd numbers between 38 and n = int[abs(n - 38)/2]
how many times can 38 go into 150
38 ÷ 15 = 2 with remainder 8
2 x 38 = 76
38
1, 2, 4, 19, 38, 76.
1, 2, 4, 19, 38, 76.
One and two will go into both numbers evenly leaving no remainders.
39+38+...+1 = 39*38/2 = 494