- a [[site]].
  - #go https://oeis.org
  - e.g.
    - [[mersenne numbers]] https://oeis.org/A000225
    - [[mersenne primes]] https://oeis.org/A001348
    - [[hex numbers]] https://oeis.org/search?q=1%2C7%2C19%2C37%2C61%2C91
    - [[hexagonal numbers]] https://oeis.org/A000384