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) |
|---|---|
| 3 | 0 |
| 4 | -1 |
| 5 | 0 |
| 6 | 0 |
| 7 | 307 |
| 8 | -1 |
| 9 | 2027 |
| 10 | 5200 |
| 11 | 18180 |
| 12 | -1 |
| 13 | 10795 |
| 14 | -1 |
| 15 | 87740 |
| 16 | -1 |
| 17 | 75150 |
| 18 | 212048 |
| 19 | 122818 |
| 20 | -1 |
| 21 | 146970 |
| 22 | 199153 |
| 23 | 585513 |