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 | 5 |
| 3 | 42 |
| 4 | 462 |
| 5 | 6006 |
| 6 | 87516 |
| 7 | 1385670 |
| 8 | 23371634 |
| 9 | 414315330 |
| 10 | 7646001090 |
| 11 | 145862174640 |
| 12 | 2861142656400 |
| 13 | 57468093927120 |
| 14 | 1178095925505960 |
| 15 | 24584089974896430 |
| 16 | 521086299271824330 |
| 17 | 11198784501894470250 |
| 18 | 243661974372798631650 |
| 19 | 5360563436201569896300 |