Re: [math-fun] Interleavings of three arithmetic progressions

On Jul 25, 2010, at 12:52 PM, Michael Kleber wrote:

1,3,9,27,75,189,447,951,1911,3621,6513,11103,18267,29013,44691,67251,98547,140865,197679,272799,370659,497403,658371,859863,1110453,1420527,1799373,2260161,2815401,3479235,4269279

Looks more n^5ish than n^6ish, at a casual glance.

The last term took something like 11 hours to count, so I think it's time to give Mma a break.

I noticed that your code recursively memorizes the results for smaller instances (dfn of shuf[n_]), so the timing should depend whether you're starting for scratch, or whether you just did a slightly smaller case --- especially if this is implemented as a polynomial time computation. But whatever, Mma probably has better things to do. Bill