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 | -3 |
| 3 | 15 |
| 4 | -85 |
| 5 | 523 |
| 6 | -3367 |
| 7 | 22371 |
| 8 | -152104 |
| 9 | 1052568 |
| 10 | -7385756 |
| 11 | 52410754 |
| 12 | -375382683 |
| 13 | 2709626768 |
| 14 | -19688989762 |
| 15 | 143885743077 |
| 16 | -1056748051734 |
| 17 | 7795106129504 |
| 18 | -57723430872280 |
| 19 | 428923406694402 |