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 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 5 |
| 6 | 15 |
| 7 | 53 |
| 8 | 222 |
| 9 | 1078 |
| 10 | 5994 |
| 11 | 37622 |
| 12 | 262776 |
| 13 | 2018305 |
| 14 | 16873364 |
| 15 | 152233518 |
| 16 | 1471613387 |
| 17 | 15150569446 |
| 18 | 165269824761 |
| 19 | 1901910625578 |
| 20 | 23003059864006 |