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 | 0 |
| 4 | 2 |
| 5 | 20 |
| 6 | 120 |
| 7 | 560 |
| 8 | 2240 |
| 9 | 8064 |
| 10 | 26880 |
| 11 | 84480 |
| 12 | 253440 |
| 13 | 732160 |
| 14 | 2050048 |
| 15 | 5591040 |
| 16 | 14909440 |
| 17 | 38993920 |
| 18 | 100270080 |
| 19 | 254017536 |
| 20 | 635043840 |
| 21 | 1568931840 |
| 22 | 3835166720 |
| 23 | 9285140480 |
| 24 | 22284337152 |
| 25 | 53057945600 |
| 26 | 125409689600 |
| 27 | 294440140800 |
| 28 | 687026995200 |
| 29 | 1593902628864 |
| 30 | 3678236835840 |
| 31 | 8446321623040 |
| 32 | 19305877995520 |
| 33 | 43937515438080 |
| 34 | 99591701659648 |