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 | 0 |
| 1 | 1 |
| 2 | -1 |
| 3 | 3 |
| 4 | -10 |
| 5 | 45 |
| 6 | -256 |
| 7 | 1743 |
| 8 | -13840 |
| 9 | 125625 |
| 10 | -1282816 |
| 11 | 14554683 |
| 12 | -181649920 |
| 13 | 2473184805 |
| 14 | -36478744576 |
| 15 | 579439207623 |
| 16 | -9861412096000 |
| 17 | 179018972217585 |
| 18 | -3452931391553536 |
| 19 | 70518070842040563 |
| 20 | -1520176422094766080 |