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 | -1 |
| 4 | -5 |
| 5 | -4 |
| 6 | 29 |
| 7 | 129 |
| 8 | -65 |
| 9 | -3689 |
| 10 | -16264 |
| 11 | 113689 |
| 12 | 2382785 |
| 13 | 7001471 |
| 14 | -398035821 |
| 15 | -7911171596 |
| 16 | 43244638645 |
| 17 | 6480598259201 |
| 18 | 124106986093951 |
| 19 | -5987117709349201 |
| 20 | -541051130050800400 |
| 21 | -4830209396684261199 |