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 | 2 |
| 2 | 9 |
| 3 | 48 |
| 4 | 275 |
| 5 | 1638 |
| 6 | 9996 |
| 7 | 62016 |
| 8 | 389367 |
| 9 | 2466750 |
| 10 | 15737865 |
| 11 | 100975680 |
| 12 | 650872404 |
| 13 | 4211628008 |
| 14 | 27341497800 |
| 15 | 177996090624 |
| 16 | 1161588834303 |
| 17 | 7596549816030 |
| 18 | 49772989810635 |
| 19 | 326658445806000 |
| 20 | 2147042307851595 |
| 21 | 14130873926790390 |
| 22 | 93115841412899760 |