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 | 30 |
| 5 | 210 |
| 6 | 1680 |
| 7 | 18480 |
| 8 | 240240 |
| 9 | 4084080 |
| 10 | 77597520 |
| 11 | 1784742960 |
| 12 | 48188059920 |
| 13 | 1397453737680 |
| 14 | 43321065868080 |
| 15 | 1602879437118960 |
| 16 | 65718056921877360 |
| 17 | 2825876447640726480 |
| 18 | 132816193039114144560 |
| 19 | 7039258231073049661680 |
| 20 | 415316235633309930039120 |
| 21 | 25334290373631905732386320 |