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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | -3 |
| 5 | -4 |
| 6 | -13 |
| 7 | 23 |
| 8 | 87 |
| 9 | 415 |
| 10 | -152 |
| 11 | -8063 |
| 12 | -38727 |
| 13 | -142471 |
| 14 | 2309453 |
| 15 | 13609844 |
| 16 | 187790979 |
| 17 | -1743980081 |
| 18 | -25547499185 |
| 19 | -575984295329 |
| 20 | 1873521429456 |
| 21 | 217675476797921 |
| 22 | 5045023692031697 |
| 23 | 65853623974941521 |
| 24 | -5934036772012185603 |
| 25 | -157454833217800083092 |