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 | 1 |
| 3 | -5 |
| 4 | -23 |
| 5 | -59 |
| 6 | 961 |
| 7 | 7351 |
| 8 | 29905 |
| 9 | -877463 |
| 10 | -9450719 |
| 11 | -52724429 |
| 12 | 2282907001 |
| 13 | 31742360365 |
| 14 | 225092745697 |
| 15 | -12992587010129 |
| 16 | -221436656404319 |
| 17 | -1905297800257199 |
| 18 | 137972958868569025 |
| 19 | 2784953660339878507 |
| 20 | 28177036295775415561 |
| 21 | -2459373614334806266859 |