Given a number N, find the Nth triangular number, i.e. 1 + 2 + 3 + ... + N
import type { Equal, Expect } from '@type-challenges/utils'
type cases = [
Expect<Equal<Triangular<0>, 0>>,
Expect<Equal<Triangular<1>, 1>>,
Expect<Equal<Triangular<3>, 6>>,
Expect<Equal<Triangular<10>, 55>>,
Expect<Equal<Triangular<20>, 210>>,
Expect<Equal<Triangular<55>, 1540>>,
Expect<Equal<Triangular<100>, 5050>>,
]