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 | 0 |
| 1 | 6 |
| 2 | 60 |
| 3 | 504 |
| 4 | 4080 |
| 5 | 32736 |
| 6 | 262080 |
| 7 | 2097024 |
| 8 | 16776960 |
| 9 | 134217216 |
| 10 | 1073740800 |
| 11 | 8589932544 |
| 12 | 68719472640 |
| 13 | 549755805696 |
| 14 | 4398046494720 |
| 15 | 35184372056064 |
| 16 | 281474976645120 |
| 17 | 2251799813554176 |
| 18 | 18014398509219840 |
| 19 | 144115188075331584 |
| 20 | 1152921504605798400 |