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 | 255 |
| 3 | 6560 |
| 4 | 65280 |
| 5 | 390624 |
| 6 | 1672800 |
| 7 | 5764800 |
| 8 | 16711680 |
| 9 | 43040160 |
| 10 | 99609120 |
| 11 | 214358880 |
| 12 | 428236800 |
| 13 | 815730720 |
| 14 | 1470024000 |
| 15 | 2562493440 |
| 16 | 4278190080 |
| 17 | 6975757440 |
| 18 | 10975240800 |
| 19 | 16983563040 |
| 20 | 25499934720 |
| 21 | 37817088000 |