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 | 0 |
| 4 | 0 |
| 5 | 6 |
| 6 | 12 |
| 7 | 84 |
| 8 | 192 |
| 9 | 882 |
| 10 | 2220 |
| 11 | 8448 |
| 12 | 22704 |
| 13 | 78078 |
| 14 | 218988 |
| 15 | 710892 |
| 16 | 2048256 |
| 17 | 6430794 |
| 18 | 18837516 |
| 19 | 58008216 |
| 20 | 171619248 |
| 21 | 522598230 |
| 22 | 1555243404 |
| 23 | 4705481220 |
| 24 | 14051590080 |
| 25 | 42357719586 |
| 26 | 126740502252 |
| 27 | 381253030704 |
| 28 | 1142062255152 |
| 29 | 3431411494062 |