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 | 2 |
| 3 | 0 |
| 4 | -4 |
| 5 | -4 |
| 6 | 12 |
| 7 | 32 |
| 8 | -40 |
| 9 | -264 |
| 10 | 56 |
| 11 | 2432 |
| 12 | 1872 |
| 13 | -24880 |
| 14 | -47344 |
| 15 | 276096 |
| 16 | 938912 |
| 17 | -3202528 |
| 18 | -18225120 |
| 19 | 36217856 |
| 20 | 364270016 |
| 21 | -323869248 |
| 22 | -7609269568 |
| 23 | -808015360 |
| 24 | 166595915136 |
| 25 | 185180268416 |
| 26 | -3813121694848 |
| 27 | -8442628405248 |
| 28 | 90698535660800 |
| 29 | 318649502602496 |
| 30 | -2220909495899904 |