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 | 0 |
| 2 | 4 |
| 3 | -4 |
| 4 | 16 |
| 5 | -28 |
| 6 | 72 |
| 7 | -148 |
| 8 | 336 |
| 9 | -716 |
| 10 | 1560 |
| 11 | -3332 |
| 12 | 7136 |
| 13 | -15164 |
| 14 | 32168 |
| 15 | -67956 |
| 16 | 143216 |
| 17 | -300972 |
| 18 | 631096 |
| 19 | -1320420 |
| 20 | 2757376 |
| 21 | -5747740 |
| 22 | 11961544 |
| 23 | -24855124 |
| 24 | 51574416 |
| 25 | -106877068 |
| 26 | 221210712 |
| 27 | -457334468 |
| 28 | 944495136 |
| 29 | -1948642556 |