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 | 3 |
| 2 | 24 |
| 3 | 76 |
| 4 | 672 |
| 5 | 2208 |
| 6 | 20224 |
| 7 | 67776 |
| 8 | 632320 |
| 9 | 2144768 |
| 10 | 20238336 |
| 11 | 69203968 |
| 12 | 658079744 |
| 13 | 2263351296 |
| 14 | 21643526144 |
| 15 | 74764042240 |
| 16 | 717975060480 |
| 17 | 2488551997440 |
| 18 | 23977645834240 |
| 19 | 83334108020736 |
| 20 | 805090608807936 |
| 21 | 2804309838266368 |