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 | 1 |
| 2 | 24 |
| 3 | 240 |
| 4 | 504 |
| 5 | 65520 |
| 6 | 131040 |
| 7 | 171864 |
| 8 | 138181680 |
| 9 | 6814407600 |
| 10 | 20174525280 |
| 11 | 45185409360 |
| 12 | 558781423200 |
| 13 | 685933859520 |
| 14 | 2601256998740400 |
| 15 | 4578654981700800 |
| 16 | 15571124394460034400 |
| 17 | 375159113055066740400 |
| 18 | 124708934978441512498800 |
| 19 | 127589793288205521873600 |
| 20 | 8644416283014847832296800 |
| 21 | 29217965124687229769336640 |