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 | 1 |
| 3 | 15 |
| 4 | 113 |
| 5 | 783 |
| 6 | 5361 |
| 7 | 36879 |
| 8 | 255985 |
| 9 | 1794063 |
| 10 | 12689393 |
| 11 | 90505231 |
| 12 | 650379249 |
| 13 | 4705157135 |
| 14 | 34244198385 |
| 15 | 250572963855 |
| 16 | 1842382110705 |
| 17 | 13605619630095 |
| 18 | 100872203796465 |
| 19 | 750556607938575 |
| 20 | 5602962592235505 |
| 21 | 41952165966643215 |
| 22 | 314983352736153585 |