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 | 4 |
| 3 | -7 |
| 4 | 22 |
| 5 | -46 |
| 6 | 130 |
| 7 | -295 |
| 8 | 790 |
| 9 | -1870 |
| 10 | 4864 |
| 11 | -11782 |
| 12 | 30148 |
| 13 | -73984 |
| 14 | 187534 |
| 15 | -463687 |
| 16 | 1168870 |
| 17 | -2902870 |
| 18 | 7293640 |
| 19 | -18161170 |
| 20 | 45541492 |
| 21 | -113576596 |
| 22 | 284470564 |
| 23 | -710118262 |
| 24 | 1777323772 |
| 25 | -4439253196 |
| 26 | 11105933440 |
| 27 | -27749232700 |
| 28 | 69403169200 |