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 | -2 |
| 3 | 0 |
| 4 | 6 |
| 5 | -18 |
| 6 | 36 |
| 7 | -54 |
| 8 | 54 |
| 9 | 0 |
| 10 | -162 |
| 11 | 486 |
| 12 | -972 |
| 13 | 1458 |
| 14 | -1458 |
| 15 | 0 |
| 16 | 4374 |
| 17 | -13122 |
| 18 | 26244 |
| 19 | -39366 |
| 20 | 39366 |
| 21 | 0 |
| 22 | -118098 |
| 23 | 354294 |
| 24 | -708588 |
| 25 | 1062882 |
| 26 | -1062882 |
| 27 | 0 |
| 28 | 3188646 |
| 29 | -9565938 |
| 30 | 19131876 |
| 31 | -28697814 |
| 32 | 28697814 |
| 33 | 0 |
| 34 | -86093442 |
| 35 | 258280326 |
| 36 | -516560652 |