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) |
|---|---|
| 2 | 0 |
| 3 | 4 |
| 4 | 16 |
| 5 | 60 |
| 6 | 224 |
| 7 | 840 |
| 8 | 3168 |
| 9 | 12012 |
| 10 | 45760 |
| 11 | 175032 |
| 12 | 671840 |
| 13 | 2586584 |
| 14 | 9984576 |
| 15 | 38630800 |
| 16 | 149768640 |
| 17 | 581690700 |
| 18 | 2262890880 |
| 19 | 8815845720 |
| 20 | 34389986400 |
| 21 | 134312002440 |
| 22 | 525129633600 |
| 23 | 2055166429680 |
| 24 | 8050465600320 |
| 25 | 31561484455800 |