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 | 6 |
| 3 | 18 |
| 4 | 60 |
| 5 | 200 |
| 6 | 700 |
| 7 | 2450 |
| 8 | 8820 |
| 9 | 31752 |
| 10 | 116424 |
| 11 | 426888 |
| 12 | 1585584 |
| 13 | 5889312 |
| 14 | 22084920 |
| 15 | 82818450 |
| 16 | 312869700 |
| 17 | 1181952200 |
| 18 | 4491418360 |
| 19 | 17067389768 |
| 20 | 65166397296 |
| 21 | 248817153312 |
| 22 | 953799087696 |
| 23 | 3656229836168 |
| 24 | 14062422446800 |
| 25 | 54086240180000 |
| 26 | 208618354980000 |