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 | -1 |
| 4 | -7 |
| 5 | 5 |
| 6 | 145 |
| 7 | -5 |
| 8 | -6095 |
| 9 | -5815 |
| 10 | 433025 |
| 11 | 956375 |
| 12 | -46676375 |
| 13 | -172917875 |
| 14 | 7108596625 |
| 15 | 38579649875 |
| 16 | -1454225641375 |
| 17 | -10713341611375 |
| 18 | 384836032842625 |
| 19 | 3663118565923375 |
| 20 | -127950804666254375 |
| 21 | -1519935859717136875 |