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 | 4 |
| 2 | 24 |
| 3 | 188 |
| 4 | 1804 |
| 5 | 20416 |
| 6 | 265640 |
| 7 | 3901320 |
| 8 | 63776280 |
| 9 | 1147796160 |
| 10 | 22540858080 |
| 11 | 479500074720 |
| 12 | 10980929163360 |
| 13 | 269298981833280 |
| 14 | 7040446188020160 |
| 15 | 195439047629422080 |
| 16 | 5740498087530831360 |
| 17 | 177855276360034736640 |
| 18 | 5796391124741936993280 |