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 | 4 |
| 2 | 72 |
| 3 | 32 |
| 4 | 14400 |
| 5 | 1728 |
| 6 | 2540160 |
| 7 | 138240 |
| 8 | 261273600 |
| 9 | 896000 |
| 10 | 10538035200 |
| 11 | 209018880 |
| 12 | 407994402816000 |
| 13 | 5633058816000 |
| 14 | 941525544960000 |
| 15 | 4723310592 |
| 16 | 8707228239790080000 |
| 17 | 6162712657920000 |
| 18 | 17473102222724628480000 |
| 19 | 107559878256230400000 |
| 20 | 14162409169997856768000000 |