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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 720 |
| 8 | 40320 |
| 9 | 1632960 |
| 10 | 60480000 |
| 11 | 2213719200 |
| 12 | 82771476480 |
| 13 | 3211179491520 |
| 14 | 130247609057280 |
| 15 | 5542874078742000 |
| 16 | 247828800444825600 |
| 17 | 11643316737494682240 |
| 18 | 574455837701776343040 |
| 19 | 29734324379435446505280 |
| 20 | 1612668074301849600000000 |