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) |
|---|---|
| 1 | 6 |
| 2 | 28 |
| 3 | 144 |
| 4 | 730 |
| 5 | 3692 |
| 6 | 18666 |
| 7 | 94384 |
| 8 | 477264 |
| 9 | 2413346 |
| 10 | 12203374 |
| 11 | 61707810 |
| 12 | 312032874 |
| 13 | 1577831334 |
| 14 | 7978491800 |
| 15 | 40344192708 |
| 16 | 204005208738 |
| 17 | 1031576601204 |
| 18 | 5216289773894 |
| 19 | 26376789637884 |
| 20 | 133377373911160 |
| 21 | 674438554337506 |