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) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 9 |
| 4 | 30 |
| 5 | 110 |
| 6 | 450 |
| 7 | 2457 |
| 8 | 11774 |
| 9 | 47910 |
| 10 | 264630 |
| 11 | 5565065 |
| 12 | 56021922 |
| 13 | 866143434 |
| 14 | 9894742130 |
| 15 | 78233264865 |
| 16 | 470058202350 |
| 17 | 24530748587102 |
| 18 | 409761902222094 |
| 19 | 10595012400106545 |
| 20 | 160826238368038490 |
| 21 | 1585844131838898330 |
| 22 | 16787211702213659322 |
| 23 | 1362379222505265018329 |