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 | 18 |
| 3 | 84 |
| 4 | 400 |
| 5 | 1932 |
| 6 | 9436 |
| 7 | 46512 |
| 8 | 231066 |
| 9 | 1155660 |
| 10 | 5813808 |
| 11 | 29396952 |
| 12 | 149305884 |
| 13 | 761282032 |
| 14 | 3894953640 |
| 15 | 19987999696 |
| 16 | 102847396416 |
| 17 | 530446714812 |
| 18 | 2741576339716 |
| 19 | 14196136939600 |
| 20 | 73631851898220 |
| 21 | 382483602131400 |
| 22 | 1989514312826400 |
| 23 | 10361255764532400 |
| 24 | 54020655931542300 |
| 25 | 281933439875693424 |