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 | 4 |
| 2 | 12 |
| 3 | 42 |
| 4 | 148 |
| 5 | 540 |
| 6 | 1990 |
| 7 | 7434 |
| 8 | 27972 |
| 9 | 106008 |
| 10 | 403764 |
| 11 | 1544796 |
| 12 | 5931486 |
| 13 | 22846252 |
| 14 | 88228998 |
| 15 | 341518606 |
| 16 | 1324627044 |
| 17 | 5146959168 |
| 18 | 20030812360 |
| 19 | 78066774400 |
| 20 | 304643526276 |
| 21 | 1190209498344 |
| 22 | 4654949367204 |
| 23 | 18223301727108 |