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 | 83 |
| 5 | 556 |
| 6 | 4435 |
| 7 | 40773 |
| 8 | 423836 |
| 9 | 4908403 |
| 10 | 62606297 |
| 11 | 871421976 |
| 12 | 13136605577 |
| 13 | 213122669141 |
| 14 | 3701085673676 |
| 15 | 68480774296803 |
| 16 | 1344611320542931 |
| 17 | 27917413103561540 |
| 18 | 611000785570868627 |
| 19 | 14056645627856206809 |
| 20 | 339081826905338009620 |
| 21 | 8557085279980716462407 |