Odd  numbers are 1,3,5,7,9,….   Now we will see the sum of elements:   Sum of first 2 odd  numbers: 1+3= 4= 2 2   Sum of first 3 odd  numbers: 1+3+5= 9= 3 2   Sum of first 4 odd  numbers: 1+3+5+7=16= 4 2   Sum of first 5 odd  numbers: 1+3+5+7+9 = 25 = 5 2                   Sum of first 6 odd  numbers: 1+3+5+7+9 +11= 36 = 6 2                 Sum of first 7 odd  numbers: 1+3+5+7+9+11+13 = 49 = 7 2                Sum of first 8 odd  numbers: 1+3+5+7+9+11+13+15 = 64 = 8 2      Sum of first n odd  numbers: 1+3+5+7+9+. . . . .  n numbers= n 2