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 | 3 |
| 2 | 10 |
| 3 | 35 |
| 4 | 125 |
| 5 | 455 |
| 6 | 1680 |
| 7 | 6270 |
| 8 | 23591 |
| 9 | 89335 |
| 10 | 340076 |
| 11 | 1300234 |
| 12 | 4989504 |
| 13 | 19206500 |
| 14 | 74132230 |
| 15 | 286802444 |
| 16 | 1111864311 |
| 17 | 4318284037 |
| 18 | 16798674426 |
| 19 | 65444081290 |
| 20 | 255290775209 |
| 21 | 997047334415 |
| 22 | 3898217039280 |
| 23 | 15256167628139 |