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 | -1 |
| 3 | -1 |
| 4 | 1 |
| 5 | 11 |
| 6 | 37 |
| 7 | 209 |
| 8 | 113 |
| 9 | 23 |
| 10 | -4381 |
| 11 | -84389 |
| 12 | -310517 |
| 13 | -4103887 |
| 14 | -25059901 |
| 15 | -274436401 |
| 16 | -13182829 |
| 17 | -104362273 |
| 18 | 1748375381 |
| 19 | 690031209911 |
| 20 | 4647089032189 |
| 21 | 112233351264271 |
| 22 | 1276100569319881 |
| 23 | 2131681036523177 |
| 24 | 71497025649480187 |
| 25 | 1365106755339875117 |