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 | 9 |
| 2 | 27 |
| 3 | 0 |
| 4 | -81 |
| 5 | 243 |
| 6 | 0 |
| 7 | -2916 |
| 8 | 10935 |
| 9 | 0 |
| 10 | -168399 |
| 11 | 682344 |
| 12 | 0 |
| 13 | -11711385 |
| 14 | 49364964 |
| 15 | 0 |
| 16 | -900438201 |
| 17 | 3887490915 |
| 18 | 0 |
| 19 | -73729998576 |
| 20 | 323480165085 |
| 21 | 0 |
| 22 | -6303914878248 |
| 23 | 27978933759300 |
| 24 | 0 |
| 25 | -556251967191492 |
| 26 | 2490404893915293 |
| 27 | 0 |
| 28 | -50276620111538700 |
| 29 | 226626845346291663 |
| 30 | 0 |