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 | 25 |
| 3 | 219 |
| 4 | 1777 |
| 5 | 13683 |
| 6 | 102025 |
| 7 | 745419 |
| 8 | 5374177 |
| 9 | 38400483 |
| 10 | 272709625 |
| 11 | 1928498619 |
| 12 | 13597146577 |
| 13 | 95668307283 |
| 14 | 672119557225 |
| 15 | 4717043931819 |
| 16 | 33080342678977 |
| 17 | 231867574534083 |
| 18 | 1624598900644825 |
| 19 | 11379821699045019 |
| 20 | 79696898865971377 |
| 21 | 558069026925080883 |