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 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 112 |
| 6 | 560 |
| 7 | 2888 |
| 8 | 15136 |
| 9 | 80160 |
| 10 | 427968 |
| 11 | 2300736 |
| 12 | 12445440 |
| 13 | 67702272 |
| 14 | 370205184 |
| 15 | 2033976960 |
| 16 | 11224014336 |
| 17 | 62186741248 |
| 18 | 345825348608 |
| 19 | 1929744008192 |
| 20 | 10802203119616 |
| 21 | 60644473282560 |
| 22 | 341383505977344 |
| 23 | 1926554113200128 |
| 24 | 10897582426832896 |
| 25 | 61775951537520640 |
| 26 | 350901756369403904 |