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 | 0 |
| 2 | 1 |
| 3 | 0 |
| 4 | -9 |
| 5 | 10 |
| 6 | 0 |
| 7 | 477 |
| 8 | -756 |
| 9 | 280 |
| 10 | 0 |
| 11 | -74601 |
| 12 | 142362 |
| 13 | -83160 |
| 14 | 15400 |
| 15 | 0 |
| 16 | 25740261 |
| 17 | -55429920 |
| 18 | 40900860 |
| 19 | -12612600 |
| 20 | 1401400 |
| 21 | 0 |
| 22 | -16591655817 |
| 23 | 38999319642 |
| 24 | -33465991104 |
| 25 | 13440707280 |
| 26 | -2572970400 |
| 27 | 190590400 |