Hopping Game (noch nicht übersetzt)
Let sk be the number of 1’s when writing the numbers from 0 to k in binary.
For example, writing 0 to 5 in binary, we have 0,1,10,11,100,101. There are seven 1’s, so s5=7.
The sequence S={sk:k≥0} starts {0,1,2,4,5,7,9,12,...}.
A game is played by two players. Before the game starts, a number n is chosen. A counter c starts at 0. At each turn, the player chooses a number from 1 to n (inclusive) and increases c by that number. The resulting value of c must be a member of S. If there are no more valid moves, then the player loses.
For example, with n=5 and starting with c=0:
Player 1 chooses 4, so c becomes 0+4=4.
Player 2 chooses 5, so c becomes 4+5=9.
Player 1 chooses 3, so c becomes 9+3=12.
etc.
Note that c must always belong to S, and each player can increase c by at most n.
Let M(n) be the highest number that the first player could choose at the start to force a win, and M(n)=0 if there is no such move. For example, M(2)=2, M(7)=1, and M(20)=4.
It can be verified that ∑M(n)3=8150 for 1≤n≤20.
Find ∑M(n)3 for 1≤n≤1000.