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 | 3 |
| 3 | 15 |
| 4 | 90 |
| 5 | 594 |
| 6 | 4158 |
| 7 | 30294 |
| 8 | 227205 |
| 9 | 1741905 |
| 10 | 13586859 |
| 11 | 107459703 |
| 12 | 859677624 |
| 13 | 6943550040 |
| 14 | 56540336040 |
| 15 | 463630755528 |
| 16 | 3824953733106 |
| 17 | 31724616256938 |
| 18 | 264371802141150 |
| 19 | 2212374554760150 |
| 20 | 18583946259985260 |
| 21 | 156636118477018620 |
| 22 | 1324287183487521060 |