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 | 2 |
| 3 | -1 |
| 4 | -1 |
| 5 | 1 |
| 6 | -1 |
| 7 | -1 |
| 8 | 7 |
| 9 | 5 |
| 10 | -2663 |
| 11 | -691 |
| 12 | 1247 |
| 13 | 7 |
| 14 | -1511 |
| 15 | -3617 |
| 16 | 1623817 |
| 17 | 43867 |
| 18 | -10405289 |
| 19 | -174611 |
| 20 | 21491081 |
| 21 | 854513 |
| 22 | -2523785339 |
| 23 | -236364091 |
| 24 | 1827648887 |
| 25 | 8553103 |
| 26 | -11254630547 |
| 27 | -23749461029 |
| 28 | 596303510772251 |
| 29 | 8615841276005 |