This challenge is inspired by a talk about Schläfli symbols, etc that I gave in a Geometry seminar. While I was putting together this challenge, I saw that Donald Knuth himself was interested in (some subset of) this problem. In October 2016, he commented on a related OEIS sequence:
If [the OEIS author] is wrong about the hyperbolic {4,5} pentominoes, the next number is probably mistaken too. I don't have [time] right now to investigate further.
Successful completion of this challenge will have you investigating something that Donald Knuth might have investigated if only he had more time, and will result in new additions (and perhaps a rare correction) to the On-Line Encyclopedia of Integer Sequences.
Challenge
This code-golf challenge will have you create a function that counts "free polyforms" on the hyperbolic plane. In particular, you will write a function that takes three positive integer parameters p, q, and n and counts the number of \$n\$-cell "free polyforms" on the tiling of the hyperbolic plane given by the Schläfli symbol \$\{p,q\}\$.
Shortest code wins.
Definitions
The Schläfli symbol \$\{p,q\}\$ describes a tiling of the hyperbolic plane by \$p\$-gons, where each vertex touches exactly \$q\$ of the polygons. As an example, see the Wikipedia page for the \$\{4,5\}\$ tiling that Donald references above.
A free polyform is a collection of regular polygons that meet at their edges, counted up to rotation and reflection.
Input
You can assume that the values of p and q which define the tiling indeed describe an actual tiling of the hyperbolic plane. This means that \$p \geq 3\$, and
- when \$p = 3\$, \$q \geq 7\$,
- when \$p = 4\$, \$q \geq 5\$,
- when \$p = 5\$, \$q \geq 4\$,
- when \$p = 6\$, \$q \geq 4\$, and
- when \$p \geq 7\$, \$q \geq 3\$.
Data
OEIS sequence A119611 claims that f(4,5,n) = A119611(n), but Donald Knuth disputes the reasoning for the value of \$A119611(5)\$. (When I counted by hand, I got Knuth's answer, and I've included it in the table below.)
| \$p\$ | \$q\$ | \$n\$ | \$f(p,q,n)\$ |
|---|---|---|---|
| 3 | 7 | 1 | 1 |
| 3 | 7 | 2 | 1 |
| 3 | 7 | 3 | 1 |
| 3 | 7 | 4 | 3 |
| 3 | 7 | 5 | 4 |
| 3 | 7 | 6 | 12 |
| 3 | 7 | 7 | 27 |
| 3 | 9 | 8 | 82 |
| 4 | 5 | 3 | 2 |
| 4 | 5 | 4 | 5 |
| 4 | 5 | 5 | 16 |
| 6 | 4 | 3 | 3 |
| 7 | 3 | 1 | 1 |
| 7 | 3 | 2 | 1 |
| 7 | 3 | 3 | 3 |
| 8 | 3 | 3 | 4 |
| 9 | 3 | 3 | 4 |
Note: these values are computed by hand, so let me know if you suspect any mistakes.
Final notes
The output of this program will result in quite a lot of new, interesting sequences for the OEIS. You are of course free to author any such sequences—but if you're not interested, I'll add the values you compute to the Encylopedia with a link to your answer.
