I calculated n(n+1)/2 and got 10/324/23

6/2700/13 or 14/424/31

12/156/19. So difficult..

AND THIS TRIAGONAL SIGN

7/140/11. Found that I could get rid of a MC6 and a ROM since the sample size is so small.

I did it in 7/211/14 :)

I used the fact that
f(an+b) = 0.5an^2+0.5a+anb+f(b)
and hardcoded sufficiently small b values.

As long as a is even, then this works while only using integers

Nvm got 14/225/15.

I got 14/315/21, with linear calculation speed of 21 power per input. Had some fun since I had more space, but if I had more I think I could do better.

I don't know how I knew about the Fibonacci sequence and not a similar concept like Triangular Numbers! This was fun to solve, if you'd like to see how I did it then check out my solution here: Solution

Fair warning, I did add a lot more wires than needed but a lot are redundant and only make it look neato.