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 | 192 |
| 5 | 1800 |
| 6 | 20880 |
| 7 | 282240 |
| 8 | 4354560 |
| 9 | 75479040 |
| 10 | 1455148800 |
| 11 | 30855686400 |
| 12 | 713712384000 |
| 13 | 17884003737600 |
| 14 | 482619020083200 |
| 15 | 13954193180928000 |
| 16 | 430360865206272000 |
| 17 | 14102295149150208000 |
| 18 | 489295008086556672000 |
| 19 | 17919783031425859584000 |