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 | 4 |
| 3 | 15 |
| 4 | 50 |
| 5 | 161 |
| 6 | 504 |
| 7 | 1555 |
| 8 | 4750 |
| 9 | 14421 |
| 10 | 43604 |
| 11 | 131495 |
| 12 | 395850 |
| 13 | 1190281 |
| 14 | 3576304 |
| 15 | 10739835 |
| 16 | 32241350 |
| 17 | 96767741 |
| 18 | 290390604 |
| 19 | 871346575 |
| 20 | 2614389250 |
| 21 | 7843866801 |
| 22 | 23532998504 |
| 23 | 70601791715 |
| 24 | 211810967550 |
| 25 | 635444087461 |
| 26 | 1906354632004 |
| 27 | 5719108635255 |
| 28 | 17157415384250 |