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 | 0 |
| 3 | 4 |
| 4 | 28 |
| 5 | 157 |
| 6 | 820 |
| 7 | 4155 |
| 8 | 20742 |
| 9 | 102725 |
| 10 | 506504 |
| 11 | 2491230 |
| 12 | 12236520 |
| 13 | 60063399 |
| 14 | 294748884 |
| 15 | 1446436680 |
| 16 | 7099442700 |
| 17 | 34855583275 |
| 18 | 171187439920 |
| 19 | 841084246980 |
| 20 | 4134129246180 |
| 21 | 20328683526575 |
| 22 | 100003531112300 |
| 23 | 492153054177155 |