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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 9 |
| 5 | 28 |
| 6 | 90 |
| 7 | 360 |
| 8 | 1526 |
| 9 | 7616 |
| 10 | 32460 |
| 11 | 190800 |
| 12 | 947760 |
| 13 | 6382464 |
| 14 | 37065600 |
| 15 | 296524800 |
| 16 | 1812861600 |
| 17 | 15283107840 |
| 18 | 105015593280 |
| 19 | 1017540576000 |
| 20 | 7304720544000 |
| 21 | 74472335308800 |
| 22 | 629300251008000 |
| 23 | 7429184791142400 |
| 24 | 62417372203929600 |
| 25 | 746041213793075200 |