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 | 1 |
| 2 | 4 |
| 3 | 24 |
| 4 | 288 |
| 5 | 3240 |
| 6 | 74160 |
| 7 | 1970640 |
| 8 | 55762560 |
| 9 | 2271628800 |
| 10 | 118676275200 |
| 11 | 5949399456000 |
| 12 | 389282684313600 |
| 13 | 31351069535385600 |
| 14 | 2431871996666112000 |
| 15 | 227068393053325824000 |
| 16 | 25547764411931553792000 |
| 17 | 2795442523571128983552000 |
| 18 | 350437557048098924371968000 |