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 | 1 |
| 3 | 0 |
| 4 | 12 |
| 5 | 60 |
| 6 | 1320 |
| 7 | 26880 |
| 8 | 898800 |
| 9 | 40446000 |
| 10 | 2568736800 |
| 11 | 225962684640 |
| 12 | 27627178692960 |
| 13 | 4686229692144000 |
| 14 | 1104514965434200320 |
| 15 | 361988888631722352000 |
| 16 | 165271302775469812521600 |
| 17 | 105278651889065640047462400 |
| 18 | 93750696652129931568573619200 |