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 | 2 |
| 3 | 3 |
| 4 | 8 |
| 5 | 10 |
| 6 | 54 |
| 7 | -42 |
| 8 | 944 |
| 9 | -5112 |
| 10 | 47160 |
| 11 | -419760 |
| 12 | 4297512 |
| 13 | -47607144 |
| 14 | 575023344 |
| 15 | -7500202920 |
| 16 | 105180931200 |
| 17 | -1578296510400 |
| 18 | 25238664189504 |
| 19 | -428528786243904 |
| 20 | 7700297625889920 |
| 21 | -146004847062359040 |
| 22 | 2913398154375730560 |
| 23 | -61031188196889482880 |