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 | 0 |
| 1 | -2 |
| 2 | 6 |
| 3 | -18 |
| 4 | 46 |
| 5 | -114 |
| 6 | 270 |
| 7 | -626 |
| 8 | 1422 |
| 9 | -3186 |
| 10 | 7054 |
| 11 | -15474 |
| 12 | 33678 |
| 13 | -72818 |
| 14 | 156558 |
| 15 | -334962 |
| 16 | 713614 |
| 17 | -1514610 |
| 18 | 3203982 |
| 19 | -6757490 |
| 20 | 14214030 |
| 21 | -29826162 |
| 22 | 62448526 |
| 23 | -130489458 |
| 24 | 272163726 |
| 25 | -566697074 |
| 26 | 1178133390 |
| 27 | -2445745266 |
| 28 | 5070447502 |
| 29 | -10498808946 |
| 30 | 21713445774 |