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 | -3 |
| 4 | -6 |
| 5 | 35 |
| 6 | 135 |
| 7 | -476 |
| 8 | -6300 |
| 9 | 14349 |
| 10 | 298515 |
| 11 | 254056 |
| 12 | -26673042 |
| 13 | -26975169 |
| 14 | 1931306377 |
| 15 | 16803854768 |
| 16 | -336040323112 |
| 17 | -1435742838615 |
| 18 | 20743481564487 |
| 19 | 843925791375728 |
| 20 | -11354618863953550 |
| 21 | -37784454009996005 |