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 | 2 |
| 2 | 4 |
| 3 | 11 |
| 4 | 28 |
| 5 | 152 |
| 6 | 726 |
| 7 | 5268 |
| 8 | 40438 |
| 9 | 365944 |
| 10 | 3628810 |
| 11 | 39974466 |
| 12 | 479001612 |
| 13 | 6228256404 |
| 14 | 87178339984 |
| 15 | 1307706805928 |
| 16 | 20922789888016 |
| 17 | 355688409760972 |
| 18 | 6402373705728018 |
| 19 | 121645133931170028 |
| 20 | 2432902008232456692 |