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 | 0 |
| 2 | -1 |
| 3 | -6 |
| 4 | -35 |
| 5 | -220 |
| 6 | -1501 |
| 7 | -10962 |
| 8 | -83495 |
| 9 | -632952 |
| 10 | -4260601 |
| 11 | -13852190 |
| 12 | 355180981 |
| 13 | 12991115436 |
| 14 | 320077652075 |
| 15 | 7153866992790 |
| 16 | 155785273182001 |
| 17 | 3395838000334352 |
| 18 | 75000970329466895 |
| 19 | 1687941779356532682 |
| 20 | 38803334491247820301 |
| 21 | 911633573138881234740 |
| 22 | 21870615120012355726259 |