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 | 7 |
| 3 | 42 |
| 4 | 230 |
| 5 | 1190 |
| 6 | 5922 |
| 7 | 28644 |
| 8 | 135564 |
| 9 | 630630 |
| 10 | 2892890 |
| 11 | 13117676 |
| 12 | 58903572 |
| 13 | 262303132 |
| 14 | 1159666900 |
| 15 | 5094808200 |
| 16 | 22259364120 |
| 17 | 96773942790 |
| 18 | 418882316490 |
| 19 | 1805951924700 |
| 20 | 7758285404100 |
| 21 | 33221013445620 |
| 22 | 141830949914940 |
| 23 | 603876402587640 |
| 24 | 2564713671647400 |