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 | -2 |
| 2 | -2 |
| 3 | -6 |
| 4 | -22 |
| 5 | -130 |
| 6 | -870 |
| 7 | -6578 |
| 8 | -56270 |
| 9 | -533346 |
| 10 | -5551534 |
| 11 | -63053074 |
| 12 | -776254350 |
| 13 | -10302652946 |
| 14 | -146717718254 |
| 15 | -2232271391058 |
| 16 | -36147843303406 |
| 17 | -620859957094930 |
| 18 | -11275285124686446 |
| 19 | -215901942195987986 |
| 20 | -4347742535086701038 |
| 21 | -91860773988102875922 |