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 | 0 |
| 2 | 1 |
| 3 | 5 |
| 4 | 25 |
| 5 | 130 |
| 6 | 700 |
| 7 | 3876 |
| 8 | 21945 |
| 9 | 126500 |
| 10 | 740025 |
| 11 | 4382625 |
| 12 | 26225628 |
| 13 | 158331880 |
| 14 | 963250600 |
| 15 | 5899491640 |
| 16 | 36345082425 |
| 17 | 225082957512 |
| 18 | 1400431689475 |
| 19 | 8749779798375 |
| 20 | 54874635255825 |
| 21 | 345329274848250 |
| 22 | 2179969531405680 |