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 | 0 |
| 2 | 1 |
| 3 | 5 |
| 4 | 26 |
| 5 | 110 |
| 6 | 490 |
| 7 | 2086 |
| 8 | 9240 |
| 9 | 40776 |
| 10 | 185820 |
| 11 | 855580 |
| 12 | 4048616 |
| 13 | 19455800 |
| 14 | 95773496 |
| 15 | 479581480 |
| 16 | 2454041920 |
| 17 | 12776826816 |
| 18 | 67849286160 |
| 19 | 366455145936 |
| 20 | 2015621873440 |
| 21 | 11268605368160 |
| 22 | 64074235576736 |
| 23 | 370040657037920 |
| 24 | 2171138049287296 |
| 25 | 12928631894588800 |
| 26 | 78139702237771200 |