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 | 3 |
| 2 | 15 |
| 3 | 99 |
| 4 | 603 |
| 5 | 3807 |
| 6 | 24759 |
| 7 | 162243 |
| 8 | 1072683 |
| 9 | 7147359 |
| 10 | 47887767 |
| 11 | 322330995 |
| 12 | 2178055899 |
| 13 | 14765637663 |
| 14 | 100380161655 |
| 15 | 684061007139 |
| 16 | 4671543976587 |
| 17 | 31962145170015 |
| 18 | 219043736154711 |
| 19 | 1503380943222867 |
| 20 | 10332034575214779 |
| 21 | 71092843087100319 |
| 22 | 489712662842798007 |