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 | -2 |
| 2 | 4 |
| 3 | -10 |
| 4 | 26 |
| 5 | -70 |
| 6 | 192 |
| 7 | -534 |
| 8 | 1500 |
| 9 | -4246 |
| 10 | 12092 |
| 11 | -34606 |
| 12 | 99442 |
| 13 | -286730 |
| 14 | 829168 |
| 15 | -2403834 |
| 16 | 6984234 |
| 17 | -20331558 |
| 18 | 59287740 |
| 19 | -173149662 |
| 20 | 506376222 |
| 21 | -1482730098 |
| 22 | 4346486256 |
| 23 | -12754363650 |
| 24 | 37461564504 |
| 25 | -110125172682 |
| 26 | 323990062452 |
| 27 | -953883382354 |
| 28 | 2810310510110 |
| 29 | -8284915984726 |