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 | -2 |
| 3 | 3 |
| 4 | -8 |
| 5 | 45 |
| 6 | -272 |
| 7 | 1743 |
| 8 | -13568 |
| 9 | 125625 |
| 10 | -1290752 |
| 11 | 14554683 |
| 12 | -181296128 |
| 13 | 2473184805 |
| 14 | -36501112832 |
| 15 | 579439207623 |
| 16 | -9859508338688 |
| 17 | 179018972217585 |
| 18 | -3453141256896512 |
| 19 | 70518070842040563 |