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PROJECT EULER · #0986

Another Infinite Game

Statement only · SolvedOriginal problem ↗

Peter is playing another game on an infinite row of squares, each square of which can hold an unlimited number of tokens.

Initially, every square contains a token.
Given positive integers c and d, each move of the game consists of the following steps:

  1. Choose two tokens X and Y such that Y is c squares to the right of X.
  2. Move both X and Y to the square that is d squares to the right of Y.

Peter's goal is to move as many tokens as possible into one square. For example, with c=2 and d=1, it is possible to move 7 tokens into one square, following these steps (where red color marks the chosen tokens):

... 1 1 1 1 1 1 1 1 ...
... 1 1 1 1 0 1 0 3 ...
... 1 1 1 0 0 0 2 3 ...
... 0 1 0 2 0 0 2 3 ...
... 0 0 0 1 2 0 2 3 ...
... 0 0 0 1 1 0 1 5 ...
... 0 0 0 1 0 0 0 7 ...

However, it is not possible to move 8 tokens into one square.

Let G(c,d) be the maximum number of tokens Peter can move into one square. For example, G(2,1)=7. You are also given that G(1,2)=7, G(3,1)=11, G(2,2)=3 and G(1,3)=15.

Find the sum of G(c,d) for all pairs of c,d with 1c,d160.

Write-up coming later

The complete problem is available here. An approach, code, and answer will be added later.