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 | 0 |
| 1 | 4 |
| 2 | 15 |
| 3 | 68 |
| 4 | 357 |
| 5 | 1939 |
| 6 | 11098 |
| 7 | 65685 |
| 8 | 397764 |
| 9 | 2453911 |
| 10 | 15353323 |
| 11 | 97163605 |
| 12 | 620646217 |
| 13 | 3995149838 |
| 14 | 25885182840 |
| 15 | 168650876819 |
| 16 | 1104127111380 |
| 17 | 7259025764932 |
| 18 | 47901523494261 |
| 19 | 317140339436292 |
| 20 | 2105877503513609 |
| 21 | 14020561559878216 |
| 22 | 93570332318306847 |
| 23 | 625829902867176558 |
| 24 | 4194084944321575624 |
| 25 | 28158446635057280702 |
| 26 | 189368274899202732322 |