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 | 5 |
| 3 | 25 |
| 4 | 219 |
| 5 | 1596 |
| 6 | 19844 |
| 7 | 208377 |
| 8 | 3394835 |
| 9 | 46799236 |
| 10 | 886886076 |
| 11 | 15668835975 |
| 12 | 366602236558 |
| 13 | 7582277939549 |
| 14 | 199035634246870 |
| 15 | 4962275379320665 |
| 16 | 150339081311823341 |
| 17 | 4214812414260868163 |
| 18 | 141823733752997729872 |
| 19 | 4533014863242019822308 |
| 20 | 169587948261109794026999 |