## Sum of Squares of First N Natural Numbers

To find the sum of squares of first N natural numbers in Dart, we may use the direct mathematical formula or  use a For loop to iterate from 1 to N and accumulate the sum of squares. In this tutorial, we will write programs using each of the said approaches.

## Dart Program

### Find the sum of squares using For Loop

In the following program, we read a number into `n`, and find the sum of squares first n natural numbers using a For Loop.

main.dart

```import 'dart:io';

void main(){
print('Enter n');

//initialize sum to 0
var sum = 0;

//accumulate the sum of squares
for(var i = 1; i <= n; i++) {
sum += i * i;
}

print('sum = \$sum');
}```

Output

```Enter n
10
sum = 385```

Output

```Enter n
3
sum = 14```

### Find the sum of squares using mathematical formula

In the following program, we read a number into `n`, and find the sum of squares of the first `n` natural numbers using the below formula.

`sum = n * (n + 1) * (2*n + 1) / 6`

main.dart

```import 'dart:io';

void main(){
print('Enter n');

var sum = n * (n + 1) * (2 * n + 1) / 6;
print('sum = \$sum');
}```

Output

```Enter n
10
sum = 55.0```

Output

```Enter n
100
sum = 338350.0```

## Summary

In this Dart Tutorial, we learned how to find the sum of squares of the first n natural numbers.