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 | 0 |
| 2 | 4 |
| 3 | 18 |
| 4 | 96 |
| 5 | 374 |
| 6 | 1380 |
| 7 | 4696 |
| 8 | 15336 |
| 9 | 48318 |
| 10 | 148448 |
| 11 | 446890 |
| 12 | 1324104 |
| 13 | 3872656 |
| 14 | 11206764 |
| 15 | 32143818 |
| 16 | 91509120 |
| 17 | 258855006 |
| 18 | 728211180 |
| 19 | 2038815272 |
| 20 | 5684262480 |
| 21 | 15789141750 |
| 22 | 43712852544 |
| 23 | 120663667538 |
| 24 | 332191809936 |
| 25 | 912339490464 |