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 | 1 |
| 2 | 1 |
| 3 | 18 |
| 4 | 18 |
| 5 | 252 |
| 6 | 252 |
| 7 | 3168 |
| 8 | 3168 |
| 9 | 37512 |
| 10 | 37512 |
| 11 | 427608 |
| 12 | 427608 |
| 13 | 4748472 |
| 14 | 4748472 |
| 15 | 51736248 |
| 16 | 51736248 |
| 17 | 555626232 |
| 18 | 555626232 |
| 19 | 5900636088 |
| 20 | 5900636088 |
| 21 | 62105724792 |
| 22 | 62105724792 |
| 23 | 648951523128 |
| 24 | 648951523128 |
| 25 | 6740563708152 |