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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 48 |
| 5 | 120 |
| 6 | 8640 |
| 7 | 5040 |
| 8 | 1935360 |
| 9 | 2177280 |
| 10 | 870912000 |
| 11 | 39916800 |
| 12 | 99325771776000 |
| 13 | 6227020800 |
| 14 | 878757175296000 |
| 15 | 941525544960000 |
| 16 | 40493130637639680000 |
| 17 | 355687428096000 |
| 18 | 20073254719690742169600000 |
| 19 | 121645100408832000 |
| 20 | 50852245289883213496320000000 |
| 21 | 1544990091272493465600000 |