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 | 55 |
| 4 | 198 |
| 5 | 681 |
| 6 | 2263 |
| 7 | 7341 |
| 8 | 23331 |
| 9 | 72928 |
| 10 | 224814 |
| 11 | 684882 |
| 12 | 2065346 |
| 13 | 6173466 |
| 14 | 18310212 |
| 15 | 53935350 |
| 16 | 157904130 |
| 17 | 459755694 |
| 18 | 1332010954 |
| 19 | 3841812480 |
| 20 | 11035346151 |
| 21 | 31579747613 |
| 22 | 90061069065 |
| 23 | 256028590665 |
| 24 | 725715896698 |
| 25 | 2051465107719 |
| 26 | 5784472106577 |
| 27 | 16271956316851 |