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# Sum of the first N terms of the series 2, 6, 12, 20, 30â€¦. in c programming

To find the sum of this series, we will first analyze this series.

The series is: 2,6,12,20,30…

## Example

For n = 6 Sum = 112 On analysis, (1+1),(2+4),(3+9),(4+16)... (1+1^{2}), (2+2^{2}), (3+3^{2}), (4+4^{2}), can be divided into two series i.e. s1:1,2,3,4,5… andS2: 1^{2},^{2},3^{2},....

Find the sum of first and second using mathematical formula

Sum1 = 1+2+3+4… , sum1 = n*(n+1)/2 Sum2 = 12+2^{2}+3^{2}+4^{2}… , sum1 = n*(n+1)*(2*n +1)/6

## Example

#include <stdio.h> int main() { int n = 3; int sum = ((n*(n+1))/2)+((n*(n+1)*(2*n+1))/6); printf("the sum series till %d is %d", n,sum); return 0; }

## Output

The sum of series till 3 is 20

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