For how many integers n where 2≤n≤100 is (n 2) odd?

https://web2.0calc.com/questions/for-how-many-integers-n-where-2-n-100-is-n2-odd 

answer is wrong.

n choose 2 is odd when n=2,3,6,7,10,11,14,15,18,19,22,23,26,27,30,31,34,35,38,39,42,43,46,47,50,51,54,55,58,59,62,63,66,67,70,71,74,75,78,79,82,83,86,86,87,90,91,94,95,98,,99

total=50 ways.

 

 

n choose 2 is even when n=4,5,8,9,12,13,16,17,20,21,24,25,28,29,32,33,36,37,40,41,44,45,48,49,52,53,55,56,57,60,61,64,65,68,69,72,73,76,77,80,81,84,85,88,89,92,93,96,97,100.