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 | 4 |
| 4 | 28 |
| 5 | 176 |
| 6 | 1600 |
| 7 | 16128 |
| 8 | 124416 |
| 9 | 1446336 |
| 10 | 35831808 |
| 11 | 1074954240 |
| 12 | 27136622592 |
| 13 | 711858585600 |
| 14 | 16840949760000 |
| 15 | 456855552000000 |
| 16 | 22466543616000000 |