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 | 33066 |
| 6 | 146858 |
| 7 | 273118 |
| 8 | -1 |
| 9 | 1274522 |
| 10 | 2117145 |
| 11 | 3613278 |
| 12 | -1 |
| 13 | 7250758 |
| 14 | -1 |
| 15 | 12911636 |
| 16 | -1 |
| 17 | 22655394 |
| 18 | 26801303 |
| 19 | 25049533 |
| 20 | -1 |
| 21 | 56922533 |
| 22 | 115715602 |
| 23 | 81539010 |
| 24 | -1 |
| 25 | 85105105 |
| 26 | -1 |
| 27 | 106555658 |
| 28 | -1 |
| 29 | 233296317 |
| 30 | 267370631 |
| 31 | 286763923 |
| 32 | -1 |
| 33 | 358322750 |