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) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 15 |
| 4 | 105 |
| 5 | 873 |
| 6 | 9997 |
| 7 | 134582 |
| 8 | 2096206 |
| 9 | 36391653 |
| 10 | 693779666 |
| 11 | 14346005530 |
| 12 | 319042302578 |
| 13 | 7579064231400 |
| 14 | 191264021808301 |
| 15 | 5103735168371201 |
| 16 | 143438421861618397 |
| 17 | 4231407420255210941 |
| 18 | 130633362289335958866 |
| 19 | 4209546674788934624394 |
| 20 | 141259712052820378949746 |