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 | 2 |
| 2 | 0 |
| 3 | 4 |
| 4 | -8 |
| 5 | 32 |
| 6 | -112 |
| 7 | 432 |
| 8 | -1696 |
| 9 | 6848 |
| 10 | -28160 |
| 11 | 117632 |
| 12 | -497664 |
| 13 | 2128128 |
| 14 | -9183488 |
| 15 | 39940864 |
| 16 | -174897664 |
| 17 | 770452480 |
| 18 | -3411959808 |
| 19 | 15181264896 |
| 20 | -67833868288 |
| 21 | 304256253952 |
| 22 | -1369404661760 |
| 23 | 6182858317824 |
| 24 | -27995941060608 |
| 25 | 127100310290432 |
| 26 | -578433619525632 |