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 | 2 |
| 3 | 3 |
| 4 | -24 |
| 5 | -475 |
| 6 | -5760 |
| 7 | -52297 |
| 8 | -155008 |
| 9 | 8781705 |
| 10 | 313344000 |
| 11 | 6966991339 |
| 12 | 102864807936 |
| 13 | 18664712365 |
| 14 | -71473582229504 |
| 15 | -3387816787568865 |
| 16 | -103478592573112320 |
| 17 | -1899945146589964783 |
| 18 | 18941335827815596032 |
| 19 | 3808766537454425974739 |
| 20 | 215681241589289359769600 |