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 | 92 |
| 4 | 630 |
| 5 | 4620 |
| 6 | 35494 |
| 7 | 282015 |
| 8 | 2298417 |
| 9 | 19108265 |
| 10 | 161418543 |
| 11 | 1381606044 |
| 12 | 11955789440 |
| 13 | 104427062460 |
| 14 | 919430773992 |
| 15 | 8151530382264 |
| 16 | 72711166411422 |
| 17 | 652075100808960 |
| 18 | 5875868463764446 |
| 19 | 53175058170610530 |
| 20 | 483082193418731280 |
| 21 | 4404057834071995110 |