2 ms·

And n(n+1)/2 was only obvious to Euler!

• sesqu 14y ago
  Hardly. It's a simple equation that has been independently discovered for as long as we've had algebra.
  • daniel-cussen 14y ago
    That's not the same as being obvious. Obvious means clear at first sight, or clear to a child. If you have to work for it, it's not obvious.
    • sesqu 14y ago
      It was clear to me as a child of maybe 8. Granted, in this day and age it's much easier to come up with elementary math, but I would say that particular equation meets the obviousness criterion of patent law, based on the aforementioned historical evidence.