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 | 0 |
| 1 | 1 |
| 2 | -1 |
| 3 | 1 |
| 4 | -2 |
| 5 | 13 |
| 6 | -64 |
| 7 | 173 |
| 8 | -720 |
| 9 | 12409 |
| 10 | -114816 |
| 11 | 370137 |
| 12 | -1491456 |
| 13 | 88556037 |
| 14 | -1263184896 |
| 15 | 2668274373 |
| 16 | 21448022016 |
| 17 | 2491377242481 |
| 18 | -50233550831616 |
| 19 | -34526890553679 |
| 20 | 5153298175033344 |
| 21 | 202383113207336829 |
| 22 | -5453228045913292800 |
| 23 | -25792743610973373219 |
| 24 | 1393299559788718325760 |