{21, 91, 221}
{21, 91, 221, 381}
{1,21, 91, 221}
{1,21, 91, 221,381}
Correct answer is A
multiples of 5 less than 20 = 5, 10 and 15
= [ 5, 10 and 15 ]x\(^2\) - x + 1
x\(^2\) - x + 1
when x = 5
5\(^2\) - 5 + 1; 25 - 5 + 1 --> 21
when x = 10
10\(^2\) - 10 + 1
100 - 9 = 91
when x = 15
15\(^2\) - 15 + 1
225 - 15 + 1 = 211