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 | 4 |
| 2 | 16 |
| 3 | 60 |
| 4 | 222 |
| 5 | 804 |
| 6 | 2872 |
| 7 | 10132 |
| 8 | 35383 |
| 9 | 122480 |
| 10 | 420752 |
| 11 | 1435736 |
| 12 | 4870132 |
| 13 | 16432216 |
| 14 | 55178416 |
| 15 | 184481816 |
| 16 | 614348813 |
| 17 | 2038435340 |
| 18 | 6740997616 |
| 19 | 22223182372 |
| 20 | 73053304378 |
| 21 | 239502956924 |
| 22 | 783241953896 |
| 23 | 2555428926860 |
| 24 | 8319101465587 |