Given two numbers N and T where, and . The task is to find the value of .
Since sum can be large, output it modulo 109+7.
Input : 3 2 Output : 38 2*3 + 3*4 + 4*5 = 38 Input : 4 2 Output : 68
In the Given Sample Case n = 3 and t = 2.
sum = 2*3+3*4+4*5.
So each term is of the form
If we multiply and divide by t! it becomes
Which is nothing but
But we know
So final expression comes out to be
But since n is so large we can not calculate it directly, we have to Simplify the above expression.
On Simplifying we get .
Below is the implementation of above approach
Time Complexity: O(T)
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- Find four factors of N with maximum product and sum equal to N | Set-2
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