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 | 4 |
| 3 | 6 |
| 4 | 80 |
| 5 | 410 |
| 6 | 5112 |
| 7 | 48818 |
| 8 | 695424 |
| 9 | 9589266 |
| 10 | 162327800 |
| 11 | 2869193162 |
| 12 | 57451559904 |
| 13 | 1225220612954 |
| 14 | 28560612445848 |
| 15 | 709917843398850 |
| 16 | 18943086191785472 |
| 17 | 536695850359985186 |
| 18 | 16151064034012994808 |
| 19 | 513345798896635886906 |
| 20 | 17206881800061632191200 |