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 | 3 |
| 4 | -8 |
| 5 | 20 |
| 6 | -48 |
| 7 | 112 |
| 8 | -256 |
| 9 | 576 |
| 10 | -1280 |
| 11 | 2816 |
| 12 | -6144 |
| 13 | 13312 |
| 14 | -28672 |
| 15 | 61440 |
| 16 | -131072 |
| 17 | 278528 |
| 18 | -589824 |
| 19 | 1245184 |
| 20 | -2621440 |
| 21 | 5505024 |
| 22 | -11534336 |
| 23 | 24117248 |
| 24 | -50331648 |
| 25 | 104857600 |
| 26 | -218103808 |
| 27 | 452984832 |
| 28 | -939524096 |
| 29 | 1946157056 |
| 30 | -4026531840 |
| 31 | 8321499136 |
| 32 | -17179869184 |