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 | 4 |
| 2 | 40 |
| 3 | 720 |
| 4 | 20160 |
| 5 | 806400 |
| 6 | 43545600 |
| 7 | 3048192000 |
| 8 | 268240896000 |
| 9 | 28970016768000 |
| 10 | 3766102179840000 |
| 11 | 579979735695360000 |
| 12 | 104396352425164800000 |
| 13 | 21714441304434278400000 |
| 14 | 5168037030455358259200000 |
| 15 | 1395369998222946729984000000 |
| 16 | 424192479459775805915136000000 |