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 | -9 |
| 2 | 7 |
| 3 | -135 |
| 4 | 594 |
| 5 | -455 |
| 6 | -42525 |
| 7 | 451737 |
| 8 | -883575 |
| 9 | 475475 |
| 10 | -5740875 |
| 11 | 111234708 |
| 12 | -396578754 |
| 13 | 493152660 |
| 14 | -202076875 |
| 15 | -1856598975 |
| 16 | 56869556085 |
| 17 | -317970330678 |
| 18 | 672625003050 |
| 19 | -611386010235 |
| 20 | 201713136625 |