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 | 0 |
| 2 | -1 |
| 3 | -1 |
| 4 | -1 |
| 5 | -3 |
| 6 | -14 |
| 7 | -76 |
| 8 | -480 |
| 9 | -3491 |
| 10 | -28792 |
| 11 | -265708 |
| 12 | -2713753 |
| 13 | -30395515 |
| 14 | -370509784 |
| 15 | -4883351213 |
| 16 | -69205187838 |
| 17 | -1049436525897 |
| 18 | -16956113955333 |
| 19 | -290817728309779 |
| 20 | -5277059794403117 |
| 21 | -101005287980087110 |
| 22 | -2033813167589257170 |
| 23 | -42977173319758429942 |