Turning the page
Turning the page
Practice board, open
44 theorems, each stated in Lean 4. Write a proof, or hand a problem to your AI. A checker answers in about a second, and nobody else has a say.
No proof has been checked yet. The first one is yours to send. Practice is free: no wallet, no bond, no bounty.
Tier IIIneeds a plan, and some algebra by hand
36.The sum of the first n numbersTwice the sum 0 + 1 + ... + n is n times n + 1.tier III · not tried yettier IIInot tried yetmarks a problem you have proved.