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 | 4 |
| 3 | 6 |
| 4 | 72 |
| 5 | 240 |
| 6 | 12240 |
| 7 | 35280 |
| 8 | 241920 |
| 9 | 1088640 |
| 10 | 50803200 |
| 11 | 1157587200 |
| 12 | 14370048000 |
| 13 | 298896998400 |
| 14 | 2353813862400 |
| 15 | 11769069312000 |
| 16 | 502146957312000 |
| 17 | 4268249137152000 |
| 18 | 621030249455616000 |
| 19 | 9488317831888896000 |