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) |
|---|---|
| 3 | 1 |
| 4 | 4 |
| 5 | 24 |
| 6 | 84 |
| 7 | 392 |
| 8 | 1344 |
| 9 | 5760 |
| 10 | 19800 |
| 11 | 81675 |
| 12 | 283140 |
| 13 | 1145144 |
| 14 | 4008004 |
| 15 | 16032016 |
| 16 | 56632576 |
| 17 | 225059328 |
| 18 | 801773856 |
| 19 | 3173688180 |
| 20 | 11392726800 |
| 21 | 44986664800 |
| 22 | 162594659920 |
| 23 | 641087516256 |
| 24 | 2331227331840 |
| 25 | 9183622822400 |
| 26 | 33577620944400 |
| 27 | 132211882468575 |
| 28 | 485773975404900 |