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 | 4 |
| 2 | 32 |
| 3 | 288 |
| 4 | 2560 |
| 5 | 26400 |
| 6 | 165888 |
| 7 | 2384928 |
| 8 | 15728640 |
| 9 | 141087744 |
| 10 | 1246080000 |
| 11 | 14758128000 |
| 12 | 85996339200 |
| 13 | 1270928131200 |
| 14 | 8810420097024 |
| 15 | 70207948800000 |
| 16 | 677066362060800 |
| 17 | 8218041445152000 |
| 18 | 43129128265187328 |
| 19 | 674757689572915200 |
| 20 | 4238841176064000000 |