Function sum

sum(formula: (n: number) => number, inf: number, sup: number): number
Returns the summation of a sequence.
Parameters
- formula: (n: number) => number
  Sequence written in summation notation
- inf: number
  Lower bound
- sup: number
  Upper bound
Returns number
Example
```
// Returns almost π²/6
const sum = Chalkboard.numb.sum((n) => 1 / (n * n), 0, 1000);
```
- Defined in Chalkboard.numb.ts:881