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 | 2 |
| 4 | 0 |
| 5 | 3 |
| 6 | -8 |
| 7 | 30 |
| 8 | -90 |
| 9 | 290 |
| 10 | -930 |
| 11 | 3000 |
| 12 | -9696 |
| 13 | 31461 |
| 14 | -102420 |
| 15 | 334467 |
| 16 | -1095510 |
| 17 | 3598464 |
| 18 | -11852026 |
| 19 | 39136629 |
| 20 | -129548493 |
| 21 | 429817733 |
| 22 | -1429178703 |
| 23 | 4761992751 |
| 24 | -15898024868 |
| 25 | 53174651133 |
| 26 | -178168302693 |
| 27 | 597971203902 |
| 28 | -2010093276240 |
| 29 | 6767100270918 |