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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 75 |
| 6 | 265 |
| 7 | 925 |
| 8 | 3201 |
| 9 | 11017 |
| 10 | 37793 |
| 11 | 129393 |
| 12 | 442497 |
| 13 | 1512225 |
| 14 | 5165953 |
| 15 | 17643457 |
| 16 | 60250113 |
| 17 | 205729921 |
| 18 | 702452225 |
| 19 | 2398414593 |
| 20 | 8188884993 |