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 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 24 |
| 5 | 14 |
| 6 | 240 |
| 7 | 878 |
| 8 | 1872 |
| 9 | 34560 |
| 10 | 143840 |
| 11 | 542880 |
| 12 | 4421376 |
| 13 | 27644438 |
| 14 | 97250652 |
| 15 | 1666163520 |
| 16 | 10523628456 |
| 17 | 30946448412 |
| 18 | 779556556800 |
| 19 | 5873176163328 |
| 20 | 15288823623792 |
| 21 | 633207380826720 |
| 22 | 6399554302310400 |
| 23 | 22325251164046200 |
| 24 | 594616643557427040 |
| 25 | 5146116019164933120 |