I need to find sum of first k term of nCr when n is in fibonaccci and r is constant.

for eg. 2C2 + 3C2 + 5C2 + 8C2 + . . . . . (till Kth term). where k is given.

The maximum value of k can be until 10^18 so loop will not work. any formula or O(logn) complexity algorithm will only work.

Can anyone please help. @vijju123 @waqar_ahmad224 @taran_1407 @galencolin @carre