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 | 7 |
| 4 | 35 |
| 5 | 215 |
| 6 | 1501 |
| 7 | 11354 |
| 8 | 88978 |
| 9 | 675569 |
| 10 | 4175664 |
| 11 | 1725333 |
| 12 | -687775083 |
| 13 | -19848956619 |
| 14 | -438027976068 |
| 15 | -8715988203509 |
| 16 | -161989586455204 |
| 17 | -2784493824166078 |
| 18 | -41530410660307610 |
| 19 | -406672888265416456 |
| 20 | 4420077014249902362 |
| 21 | 456572861717941696791 |