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 | 4 |
| 2 | 24 |
| 3 | 168 |
| 4 | 1284 |
| 5 | 10384 |
| 6 | 87360 |
| 7 | 756704 |
| 8 | 6703168 |
| 9 | 60444928 |
| 10 | 552990592 |
| 11 | 5120101760 |
| 12 | 47887472000 |
| 13 | 451759449600 |
| 14 | 4293634467840 |
| 15 | 41073654689280 |
| 16 | 395170166443008 |
| 17 | 3821262491103232 |
| 18 | 37118973530660864 |
| 19 | 362035991963869184 |
| 20 | 3544080121528001536 |