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 | 2 |
| 2 | 9 |
| 3 | 60 |
| 4 | 504 |
| 5 | 6336 |
| 6 | 89856 |
| 7 | 1645056 |
| 8 | 33094656 |
| 9 | 801239040 |
| 10 | 24246190080 |
| 11 | 777550233600 |
| 12 | 29697402470400 |
| 13 | 1250501433753600 |
| 14 | 55083063155097600 |
| 15 | 2649111037319577600 |
| 16 | 143390180403000115200 |
| 17 | 8619643674791667302400 |
| 18 | 534710099148093259776000 |
| 19 | 36412881178052121329664000 |