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 | 4 |
| 4 | 15 |
| 5 | 70 |
| 6 | 401 |
| 7 | 2715 |
| 8 | 21116 |
| 9 | 185346 |
| 10 | 1812264 |
| 11 | 19532171 |
| 12 | 230045569 |
| 13 | 2939471158 |
| 14 | 40499380397 |
| 15 | 598490843643 |
| 16 | 9442855533027 |
| 17 | 158430131720784 |
| 18 | 2816535675036147 |
| 19 | 52888281009012093 |
| 20 | 1046012668844905827 |