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 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 12 |
| 5 | 64 |
| 6 | 425 |
| 7 | 3198 |
| 8 | 27216 |
| 9 | 258144 |
| 10 | 2701737 |
| 11 | 30933770 |
| 12 | 384675148 |
| 13 | 5163521856 |
| 14 | 74417353985 |
| 15 | 1146203362822 |
| 16 | 18790377267840 |
| 17 | 326682354342336 |
| 18 | 6003886529652657 |
| 19 | 116305541572943826 |
| 20 | 2368629865508978284 |