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 | -1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 10 |
| 6 | 10 |
| 7 | 70 |
| 8 | 42 |
| 9 | 378 |
| 10 | 168 |
| 11 | 1848 |
| 12 | 660 |
| 13 | 8580 |
| 14 | 2574 |
| 15 | 38610 |
| 16 | 10010 |
| 17 | 170170 |
| 18 | 38896 |
| 19 | 739024 |
| 20 | 151164 |
| 21 | 3174444 |
| 22 | 587860 |
| 23 | 13520780 |
| 24 | 2288132 |
| 25 | 57203300 |
| 26 | 8914800 |
| 27 | 240699600 |
| 28 | 34767720 |
| 29 | 1008263880 |
| 30 | 135727830 |
| 31 | 4207562730 |
| 32 | 530365050 |
| 33 | 17502046650 |
| 34 | 2074316640 |