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 | -6 |
| 2 | 12 |
| 3 | -24 |
| 4 | 102 |
| 5 | -312 |
| 6 | 840 |
| 7 | -2544 |
| 8 | 7788 |
| 9 | -23406 |
| 10 | 69816 |
| 11 | -208968 |
| 12 | 628536 |
| 13 | -1886712 |
| 14 | 5654784 |
| 15 | -16961856 |
| 16 | 50900934 |
| 17 | -152709936 |
| 18 | 458084244 |
| 19 | -1374231912 |
| 20 | 4122828408 |
| 21 | -12368549040 |
| 22 | 37105252680 |
| 23 | -111315549552 |
| 24 | 333947845416 |
| 25 | -1001844169854 |
| 26 | 3005528872008 |