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 | 1 |
| 3 | 1 |
| 4 | 5 |
| 5 | 5 |
| 6 | 210 |
| 7 | 210 |
| 8 | 850 |
| 9 | 7735 |
| 10 | 806806 |
| 11 | 806806 |
| 12 | 3229590 |
| 13 | 3229590 |
| 14 | 161479500 |
| 15 | 1455090000 |
| 16 | 23286770000 |
| 17 | 23286770000 |
| 18 | 838446909300 |
| 19 | 838446909300 |
| 20 | 83973923013750 |
| 21 | 83973923013750 |
| 22 | 10244818607677500 |
| 23 | 10244818607677500 |