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 | 0 |
| 3 | 0 |
| 4 | 3 |
| 5 | -3 |
| 6 | 3 |
| 7 | -3 |
| 8 | 21 |
| 9 | -39 |
| 10 | 57 |
| 11 | -75 |
| 12 | 219 |
| 13 | -489 |
| 14 | 885 |
| 15 | -1407 |
| 16 | 3000 |
| 17 | -6609 |
| 18 | 13179 |
| 19 | -23655 |
| 20 | 46353 |
| 21 | -96960 |
| 22 | 198534 |
| 23 | -381504 |
| 24 | 742638 |
| 25 | -1504011 |
| 26 | 3071973 |
| 27 | -6096117 |
| 28 | 12008415 |
| 29 | -24042522 |
| 30 | 48733248 |
| 31 | -97896198 |
| 32 | 195048966 |
| 33 | -390235269 |