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 | 2 |
| 2 | 4 |
| 3 | 16 |
| 4 | 80 |
| 5 | 448 |
| 6 | 2688 |
| 7 | 16896 |
| 8 | 109824 |
| 9 | 732160 |
| 10 | 4978688 |
| 11 | 34398208 |
| 12 | 240787456 |
| 13 | 1704034304 |
| 14 | 12171673600 |
| 15 | 87636049920 |
| 16 | 635361361920 |
| 17 | 4634400522240 |
| 18 | 33985603829760 |
| 19 | 250420238745600 |
| 20 | 1853109766717440 |
| 21 | 13765958267043840 |
| 22 | 102618961627054080 |
| 23 | 767411365211013120 |