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 | 5 |
| 2 | 20 |
| 3 | 120 |
| 4 | 600 |
| 5 | 3120 |
| 6 | 15480 |
| 7 | 78120 |
| 8 | 390000 |
| 9 | 1953000 |
| 10 | 9762480 |
| 11 | 48828120 |
| 12 | 244124400 |
| 13 | 1220703120 |
| 14 | 6103437480 |
| 15 | 30517574880 |
| 16 | 152587500000 |
| 17 | 762939453120 |
| 18 | 3814695297000 |
| 19 | 19073486328120 |
| 20 | 95367421874400 |
| 21 | 476837158124880 |
| 22 | 2384185742187480 |
| 23 | 11920928955078120 |