find out a pattern for the relationship between the number of odd numbers and sum can be known

1 = 1²

1 + 3 = 4 = 2²

1 + 3 + 5 = 3²

1 + 3 + 5 + 7 = 4²

following the same pattern we can conclude that

1 + 3 + 5 + 7 + .... + (2n - 1) = n²