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 | 1 |
| 1 | 18 |
| 2 | 180 |
| 3 | 1320 |
| 4 | 7920 |
| 5 | 41184 |
| 6 | 192192 |
| 7 | 823680 |
| 8 | 3294720 |
| 9 | 12446720 |
| 10 | 44808192 |
| 11 | 154791936 |
| 12 | 515973120 |
| 13 | 1666990080 |
| 14 | 5239111680 |
| 15 | 16066609152 |
| 16 | 48199827456 |
| 17 | 141764198400 |
| 18 | 409541017600 |
| 19 | 1163958681600 |
| 20 | 3259084308480 |
| 21 | 9001280471040 |