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 | 5 |
| 2 | 28 |
| 3 | 132 |
| 4 | 574 |
| 5 | 2380 |
| 6 | 9560 |
| 7 | 37536 |
| 8 | 144872 |
| 9 | 551696 |
| 10 | 2078464 |
| 11 | 7761600 |
| 12 | 28771168 |
| 13 | 105985984 |
| 14 | 388336256 |
| 15 | 1416262656 |
| 16 | 5144067200 |
| 17 | 18616720640 |
| 18 | 67159278592 |
| 19 | 241579840512 |
| 20 | 866744413696 |
| 21 | 3102440074240 |
| 22 | 11081272653824 |