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 | 0 |
| 1 | 1 |
| 2 | 5 |
| 3 | 20 |
| 4 | 87 |
| 5 | 365 |
| 6 | 1552 |
| 7 | 6565 |
| 8 | 27825 |
| 9 | 117844 |
| 10 | 499235 |
| 11 | 2114729 |
| 12 | 8958240 |
| 13 | 37947545 |
| 14 | 160748653 |
| 15 | 680941780 |
| 16 | 2884516383 |
| 17 | 12219006325 |
| 18 | 51760543280 |
| 19 | 219261176861 |
| 20 | 928805254905 |
| 21 | 3934482189716 |
| 22 | 16666734024715 |
| 23 | 70601418270865 |