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 | 0 |
| 3 | 1 |
| 4 | 0 |
| 5 | 3 |
| 6 | -3 |
| 7 | 15 |
| 8 | -30 |
| 9 | 101 |
| 10 | -261 |
| 11 | 807 |
| 12 | -2308 |
| 13 | 7065 |
| 14 | -21171 |
| 15 | 65337 |
| 16 | -200934 |
| 17 | 627249 |
| 18 | -1962034 |
| 19 | 6192066 |
| 20 | -19610346 |
| 21 | 62482527 |
| 22 | -199807110 |
| 23 | 641837193 |
| 24 | -2068695927 |
| 25 | 6691611633 |
| 26 | -21710041944 |
| 27 | 70645706963 |
| 28 | -230488840446 |
| 29 | 753903842400 |
| 30 | -2471624380458 |
| 31 | 8120879664294 |
| 32 | -26736570257010 |