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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 8 |
| 5 | 39 |
| 6 | 235 |
| 7 | 1644 |
| 8 | 13152 |
| 9 | 118368 |
| 10 | 1183681 |
| 11 | 13020490 |
| 12 | 156245880 |
| 13 | 2031196439 |
| 14 | 28436750147 |
| 15 | 426551252206 |
| 16 | 6824820035296 |
| 17 | 116021940600031 |
| 18 | 2088394930800558 |
| 19 | 39679503685210601 |
| 20 | 793590073704212020 |