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 | 0 |
| 2 | 4 |
| 3 | 12 |
| 4 | 112 |
| 5 | 960 |
| 6 | 10848 |
| 7 | 141120 |
| 8 | 2122496 |
| 9 | 36094464 |
| 10 | 685578240 |
| 11 | 14385761280 |
| 12 | 330532435968 |
| 13 | 8253827112960 |
| 14 | 222587077558272 |
| 15 | 6447285982126080 |
| 16 | 199630453605335040 |
| 17 | 6580280144225894400 |
| 18 | 230056747973625249792 |
| 19 | 8503148524089755566080 |