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 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 24 |
| 5 | 110 |
| 6 | 600 |
| 7 | 3836 |
| 8 | 28224 |
| 9 | 235224 |
| 10 | 2191680 |
| 11 | 22584672 |
| 12 | 255087360 |
| 13 | 3134139840 |
| 14 | 41620400640 |
| 15 | 594082771200 |
| 16 | 9070900715520 |
| 17 | 147531542054400 |
| 18 | 2546434166169600 |
| 19 | 46489412442009600 |
| 20 | 895079522340864000 |
| 21 | 18125736166340812800 |
| 22 | 385129713617510400000 |