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 | 1 |
| 1 | 0 |
| 2 | 4 |
| 3 | 0 |
| 4 | 16 |
| 5 | 0 |
| 6 | 136 |
| 7 | 0 |
| 8 | 1128 |
| 9 | 384 |
| 10 | 8120 |
| 11 | 6912 |
| 12 | 60904 |
| 13 | 75136 |
| 14 | 491960 |
| 15 | 720640 |
| 16 | 4023592 |
| 17 | 6828928 |
| 18 | 32819320 |
| 19 | 63472640 |
| 20 | 270471784 |
| 21 | 574543744 |
| 22 | 2256221368 |
| 23 | 5119155712 |
| 24 | 18940876712 |
| 25 | 45266369152 |
| 26 | 159625747960 |
| 27 | 397949457408 |
| 28 | 1350573713256 |