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 | 4 |
| 2 | 22 |
| 3 | 136 |
| 4 | 868 |
| 5 | 5584 |
| 6 | 35992 |
| 7 | 232096 |
| 8 | 1496848 |
| 9 | 9653824 |
| 10 | 62262112 |
| 11 | 401558656 |
| 12 | 2589848128 |
| 13 | 16703198464 |
| 14 | 107727106432 |
| 15 | 694784866816 |
| 16 | 4481007870208 |
| 17 | 28900214293504 |
| 18 | 186391635645952 |
| 19 | 1202130942232576 |
| 20 | 7753131181401088 |