Problem #204
Combination Addition
S(N) = \sum_{n=0,k=0}^{2k \leq n \leq N} {{n-k} \choose k}
Find S(10^{18}) modulo 10^9+7.
n \choose k represents the binomial coefficient.
S(N) = \sum_{n=0,k=0}^{2k \leq n \leq N} {{n-k} \choose k}
Find S(10^{18}) modulo 10^9+7.
n \choose k represents the binomial coefficient.