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 | 2 |
| 2 | 4 |
| 3 | 14 |
| 4 | 60 |
| 5 | 286 |
| 6 | 1456 |
| 7 | 7752 |
| 8 | 42636 |
| 9 | 240350 |
| 10 | 1381380 |
| 11 | 8064030 |
| 12 | 47682960 |
| 13 | 284997384 |
| 14 | 1719031840 |
| 15 | 10450528048 |
| 16 | 63967345068 |
| 17 | 393895175646 |
| 18 | 2438398706380 |
| 19 | 15166284983850 |
| 20 | 94730949283740 |
| 21 | 593966352738990 |