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 | 0 |
| 1 | 4 |
| 2 | 12 |
| 3 | 56 |
| 4 | 200 |
| 5 | 792 |
| 6 | 2968 |
| 7 | 11440 |
| 8 | 43632 |
| 9 | 167960 |
| 10 | 646184 |
| 11 | 2496144 |
| 12 | 9655984 |
| 13 | 37442160 |
| 14 | 145416240 |
| 15 | 565722720 |
| 16 | 2203937120 |
| 17 | 8597496600 |
| 18 | 33577908232 |
| 19 | 131282408400 |
| 20 | 513791254704 |
| 21 | 2012616400080 |
| 22 | 7890369761872 |
| 23 | 30957699535776 |