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 | 10093613546512321 |
| 5 | -1 |
| 6 | -1 |
| 7 | 7700031346933907521 |
| 8 | -1 |
| 9 | 5344962129269790721 |
| 10 | -1 |
| 11 | 20453982425165652721 |
| 12 | -1 |
| 13 | 8163195338222675521 |
| 14 | -1 |
| 15 | 2467958104789157112721 |
| 16 | -1 |
| 17 | -1 |
| 18 | -1 |
| 19 | -1 |
| 20 | 14666767069023896053921 |
| 21 | 212170739123852995921 |
| 22 | 287954235303137500060321 |
| 23 | -1 |
| 24 | 84769922583214545304321 |