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 | -3 |
| 6 | -5 |
| 7 | -13 |
| 8 | 11 |
| 9 | 131 |
| 10 | 389 |
| 11 | 2311 |
| 12 | 9 |
| 13 | -81511 |
| 14 | -484247 |
| 15 | -5751815 |
| 16 | -17124617 |
| 17 | 710017141 |
| 18 | 9644648819 |
| 19 | 204006839259 |
| 20 | 2405317965859 |
| 21 | -84560118880501 |
| 22 | -2988387877551859 |
| 23 | -105333970856330737 |
| 24 | -3722531175803860975 |
| 25 | 130866937507290027313 |