EASY TO REMEMBER THE SQUARES OF NUMBER 11 TO 30

1- 2469-four times(no of letters)-11 to 14
2-258-three times- 15 to 17
3-26-two times- 18 to 19
4-048-three times-20 to 22
5-27-two times-23 to 24
6-27-two times-25 to 26
7-28-two times-27 to 28
8-4-one time-29
9-0-one time-30

Now take square of 11- 1 (2) the second 1 in 11 square 1 so it is 121
Now take 12-1 (4) the second number 2 square 4 so 144
Now take 13  - 1 (6) the square of number 3 is 9 so 169
Its up to 14  we mention above 2469 for four times 11 to 14(2 for 11,4 for 12,6 for 13,...)

Take square of 15- 2 (2) square of 5 is 25 take last digit only so 225
Take square of 29- 8th row (4) first number 81 second number 9 square take last digit only so 841.