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 | 8 |
| 5 | -22 |
| 6 | 62 |
| 7 | -182 |
| 8 | 550 |
| 9 | -1694 |
| 10 | 5294 |
| 11 | -16758 |
| 12 | 53635 |
| 13 | -173260 |
| 14 | 564129 |
| 15 | -1849448 |
| 16 | 6099972 |
| 17 | -20227036 |
| 18 | 67390803 |
| 19 | -225485432 |
| 20 | 757361764 |
| 21 | -2552692848 |
| 22 | 8631144354 |
| 23 | -29268108530 |
| 24 | 99511629658 |
| 25 | -339167845294 |
| 26 | 1158607479710 |
| 27 | -3966129297519 |
| 28 | 13603228472518 |