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 | 5 |
| 5 | 49 |
| 6 | 259 |
| 7 | 741 |
| 8 | -3263 |
| 9 | -76915 |
| 10 | -782089 |
| 11 | -5173763 |
| 12 | -9197123 |
| 13 | 389152919 |
| 14 | 8099637883 |
| 15 | 102525854939 |
| 16 | 853355714673 |
| 17 | 931100151549 |
| 18 | -140777397537929 |
| 19 | -3587404181388531 |
| 20 | -58439969237350259 |
| 21 | -649453301904349909 |
| 22 | -2064509243175655605 |
| 23 | 131896195608069986079 |