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 | -1 |
| 3 | -1 |
| 4 | 1 |
| 5 | 139 |
| 6 | 151 |
| 7 | -1429 |
| 8 | -19039 |
| 9 | -170281 |
| 10 | 517231 |
| 11 | 12144439 |
| 12 | 108063649 |
| 13 | 294730019 |
| 14 | -12338255929 |
| 15 | -161010756061 |
| 16 | -834576525119 |
| 17 | 10909293532591 |
| 18 | 350211422028511 |
| 19 | 3176429907556079 |
| 20 | -8268487440910399 |
| 21 | -816508001025525061 |
| 22 | -14017265801126968841 |
| 23 | -55997107943920795301 |