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 | 0 |
| 3 | 2 |
| 4 | 14 |
| 5 | 94 |
| 6 | 644 |
| 7 | 4808 |
| 8 | 39556 |
| 9 | 360260 |
| 10 | 3619304 |
| 11 | 39881104 |
| 12 | 478861448 |
| 13 | 6226452296 |
| 14 | 87175900720 |
| 15 | 1307664018464 |
| 16 | 20922743681264 |
| 17 | 355687216296688 |
| 18 | 6402372708414176 |
| 19 | 121645095599130560 |
| 20 | 2432901984417975904 |
| 21 | 51090942051756747104 |
| 22 | 1124000727158723041088 |
| 23 | 25852016735627132757376 |