Properties of even numbers and odd numbers

properties 1. Odd numbers

→ 1+3=2²=4               (number of terms 2)

     1+3+5=3²=9           (number of terms 3)

     1+3+5+.........=n²     (number of terms n)
 
  properties 2.Even numbers

    →2+4=2(2+1)=6            (number of terms 2)

      2+4+6=3(3+1)=12       (number of terms 3)

    2+4+6+...........=n(n+1)  (number of terms n)


Properties 3.

          →   1+2+1=2²=4           (middle term 2)

               1+2+3+2+1=3²=9     (middle term 3)

          1+2+3+4+3+2+1=4²=16 (middle term 4)
 1+2+3.....+n+..........+3+2+1=n² (middle term n)

properties 4.

→         1²=1    (one digit)

            11²=121  (two digits)

         111²=12321 (three digits)

     1111²=1234321 (four digits)