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 | 3 |
| 4 | 7 |
| 5 | -13 |
| 6 | -89 |
| 7 | -45 |
| 8 | 1191 |
| 9 | 4723 |
| 10 | -6873 |
| 11 | -143597 |
| 12 | -499289 |
| 13 | 1843891 |
| 14 | 28132391 |
| 15 | 104223059 |
| 16 | -508838745 |
| 17 | -8597456141 |
| 18 | -39770287321 |
| 19 | 158845792147 |
| 20 | 3788893515687 |
| 21 | 23979078221619 |
| 22 | -38626203043289 |
| 23 | -2200108609291821 |
| 24 | -19878849864738137 |
| 25 | -27269435066568845 |