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 | -3 |
| 2 | 0 |
| 3 | 9 |
| 4 | 27 |
| 5 | 0 |
| 6 | -324 |
| 7 | -1215 |
| 8 | 0 |
| 9 | 18711 |
| 10 | 75816 |
| 11 | 0 |
| 12 | -1301265 |
| 13 | -5484996 |
| 14 | 0 |
| 15 | 100048689 |
| 16 | 431943435 |
| 17 | 0 |
| 18 | -8192222064 |
| 19 | -35942240565 |
| 20 | 0 |
| 21 | 700434986472 |
| 22 | 3108770417700 |
| 23 | 0 |
| 24 | -61805774132388 |
| 25 | -276711654879477 |
| 26 | 0 |
| 27 | 5586291123504300 |
| 28 | 25180760594032407 |
| 29 | 0 |
| 30 | -514555201693265040 |