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 | 4 |
| 3 | 15 |
| 4 | 82 |
| 5 | 475 |
| 6 | 3456 |
| 7 | 26719 |
| 8 | 239996 |
| 9 | 2313609 |
| 10 | 24846640 |
| 11 | 285861301 |
| 12 | 3586817928 |
| 13 | 47988744115 |
| 14 | 690525294018 |
| 15 | 10547453864445 |
| 16 | 171595180564816 |
| 17 | 2949836193259105 |
| 18 | 53630566660122696 |
| 19 | 1025856767305899229 |
| 20 | 20638503314068334480 |