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 | 8 |
| 2 | 56 |
| 3 | 504 |
| 4 | 4032 |
| 5 | 32760 |
| 6 | 261576 |
| 7 | 2097144 |
| 8 | 16773120 |
| 9 | 134217216 |
| 10 | 1073709000 |
| 11 | 8589934584 |
| 12 | 68719210560 |
| 13 | 549755813880 |
| 14 | 4398044413896 |
| 15 | 35184372055560 |
| 16 | 281474959933440 |
| 17 | 2251799813685240 |
| 18 | 18014398375002624 |
| 19 | 144115188075855864 |
| 20 | 1152921503533101120 |