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 | 84 |
| 2 | 2520 |
| 3 | 41580 |
| 4 | 457380 |
| 5 | 3737448 |
| 6 | 24293412 |
| 7 | 131589315 |
| 8 | 614083470 |
| 9 | 2530768240 |
| 10 | 9386849472 |
| 11 | 31803696288 |
| 12 | 99604982880 |
| 13 | 291153026880 |
| 14 | 800670823920 |
| 15 | 2085276513474 |
| 16 | 5172303508911 |
| 17 | 12276881393700 |
| 18 | 27999904933000 |
| 19 | 61578738292500 |
| 20 | 130994770549500 |
| 21 | 270273795363000 |