This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 33 |
| 3 | 172 |
| 4 | 864 |
| 5 | 4224 |
| 6 | 20224 |
| 7 | 95232 |
| 8 | 442368 |
| 9 | 2031616 |
| 10 | 9240576 |
| 11 | 41680896 |
| 12 | 186646528 |
| 13 | 830472192 |
| 14 | 3674210304 |
| 15 | 16173236224 |
| 16 | 70866960384 |
| 17 | 309237645312 |
| 18 | 1344324763648 |
| 19 | 5823975653376 |
| 20 | 25151328485376 |
| 21 | 108301895335936 |