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) |
|---|---|
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 28 |
| 7 | 120 |
| 8 | 501 |
| 9 | 2020 |
| 10 | 8062 |
| 11 | 31992 |
| 12 | 126556 |
| 13 | 499478 |
| 14 | 1968504 |
| 15 | 7751812 |
| 16 | 30513489 |
| 17 | 120090702 |
| 18 | 472636988 |
| 19 | 1860354732 |
| 20 | 7323975621 |
| 21 | 28840527086 |
| 22 | 113600162826 |
| 23 | 447592682400 |
| 24 | 1764087889221 |
| 25 | 6954932056860 |
| 26 | 27428450072466 |