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 | 2 |
| 1 | 6 |
| 2 | 10 |
| 3 | 28 |
| 4 | 126 |
| 5 | 520 |
| 6 | 1394 |
| 7 | 4440 |
| 8 | 11765 |
| 9 | 35702 |
| 10 | 98202 |
| 11 | 271718 |
| 12 | 736814 |
| 13 | 2012631 |
| 14 | 5478367 |
| 15 | 14867499 |
| 16 | 40448112 |
| 17 | 109944053 |
| 18 | 298170203 |
| 19 | 810416222 |
| 20 | 2200884471 |
| 21 | 5980529528 |