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 | 2 |
| 1 | 4 |
| 2 | 24 |
| 3 | 432 |
| 4 | 120 |
| 5 | 8640 |
| 6 | 24192 |
| 7 | 313600 |
| 8 | 2073600 |
| 9 | 78382080 |
| 10 | 532224000 |
| 11 | 2212987392000 |
| 12 | 237758976000 |
| 13 | 135998134272000 |
| 14 | 33798352896000 |
| 15 | 28245766348800000 |
| 16 | 17072996548608000 |
| 17 | 9142589651779584000 |
| 18 | 3606419447414784000 |
| 19 | 16427702944441958400000 |
| 20 | 177473799122780160000 |