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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 6 |
| 6 | 0 |
| 7 | 120 |
| 8 | 30 |
| 9 | 840 |
| 10 | 0 |
| 11 | 362880 |
| 12 | 0 |
| 13 | 39916800 |
| 14 | 0 |
| 15 | 0 |
| 16 | 64864800 |
| 17 | 1307674368000 |
| 18 | 0 |
| 19 | 355687428096000 |
| 20 | 0 |
| 21 | 0 |
| 22 | 0 |
| 23 | 51090942171709440000 |
| 24 | 0 |
| 25 | 1292600836944248832000 |
| 26 | 0 |
| 27 | 35905578804006912000000 |
| 28 | 0 |