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 | 6 |
| 5 | 31 |
| 6 | 255 |
| 7 | 2788 |
| 8 | 37333 |
| 9 | 578799 |
| 10 | 10134071 |
| 11 | 197394232 |
| 12 | 4231417728 |
| 13 | 98991987830 |
| 14 | 2510081238264 |
| 15 | 68583045013542 |
| 16 | 2009094843480565 |
| 17 | 62824038815664719 |
| 18 | 2088829704241946181 |
| 19 | 73591470349452760456 |
| 20 | 2738742863175749456078 |