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) |
|---|---|
| 1 | -1 |
| 2 | -1 |
| 3 | -1 |
| 4 | -1 |
| 5 | -1 |
| 6 | -1 |
| 7 | -1 |
| 8 | -1 |
| 9 | -1 |
| 10 | -1 |
| 11 | 9 |
| 12 | 18 |
| 13 | 810 |
| 14 | 1017 |
| 15 | 1719 |
| 16 | 1989 |
| 17 | 989100 |
| 18 | 8910027 |
| 19 | 91002726 |
| 20 | 100272636 |
| 21 | 272636199999999999 |
| 22 | 7263619999999999911 |
| 23 | 26361999999999991116 |
| 24 | 636199999999999111620 |
| 25 | 3619999999999911162015 |
| 26 | 61999999999991116201512 |
| 27 | 199999999999111620151224 |
| 28 | 9999999999111620151224199 |