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 | 0 |
| 3 | -1 |
| 4 | -2 |
| 5 | -3 |
| 6 | -3 |
| 7 | -6 |
| 8 | -15 |
| 9 | -138 |
| 10 | -26 |
| 11 | -527 |
| 12 | -3474 |
| 13 | -19550 |
| 14 | -20014 |
| 15 | 3084 |
| 16 | -1253696 |
| 17 | 7121000 |
| 18 | -18636176 |
| 19 | -44667415 |
| 20 | 94933922 |
| 21 | -848322099 |