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 | -1 |
| 2 | -2 |
| 3 | -2 |
| 4 | 8 |
| 5 | 88 |
| 6 | 656 |
| 7 | 4912 |
| 8 | 40064 |
| 9 | 362368 |
| 10 | 3627776 |
| 11 | 39914752 |
| 12 | 478997504 |
| 13 | 6227012608 |
| 14 | 87178274816 |
| 15 | 1307674335232 |
| 16 | 20922789822464 |
| 17 | 355687427964928 |
| 18 | 6402373705465856 |
| 19 | 121645100408307712 |
| 20 | 2432902008175591424 |
| 21 | 51090942171707342848 |
| 22 | 1124000727777603485696 |