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) |
|---|---|
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 114 |
| 6 | 528 |
| 7 | 2334 |
| 8 | 9528 |
| 9 | 36834 |
| 10 | 135918 |
| 11 | 484206 |
| 12 | 1678152 |
| 13 | 5694786 |
| 14 | 19007808 |
| 15 | 62625054 |
| 16 | 204215340 |
| 17 | 660445914 |
| 18 | 2121665016 |
| 19 | 6778399914 |
| 20 | 21557206332 |
| 21 | 68294432778 |
| 22 | 215651021484 |
| 23 | 679023425238 |
| 24 | 2132750062560 |
| 25 | 6684084844362 |
| 26 | 20907052386534 |
| 27 | 65279503654446 |