+165 For how many integers n where 2<=n<=100 is n choose 2 odd?
Please don't leave an answer unexplained, it doesn't understand me help the problem.
+515 this question was answered here: https://web2.0calc.com/questions/for-how-many-integers-n-where-2-n-100-is-n2-odd
+129850 Looking at Pascal's Triangle, it appears that every
n = 2, 6.10 , 14...... = 2 + 4(p - 1) = 4p - 2
and
n = 3, 7, 11 , 15 ..... = 3 + 4(q - 1) = 4q - 1
Will have the result that C(n, 2) is odd
So
4p - 2 = 98 and 4q - 1 = 99
4p = 100 4q = 100
p = 100 / 4 = 25 q = 100 / 4 = 25
So
p + q = 25 + 25 = 50 values of n will have C( n , 2) = odd
