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 | 6 |
| 5 | -6 |
| 6 | 6 |
| 7 | -6 |
| 8 | 78 |
| 9 | -150 |
| 10 | 222 |
| 11 | -294 |
| 12 | 1374 |
| 13 | -3462 |
| 14 | 6558 |
| 15 | -10662 |
| 16 | 30894 |
| 17 | -82374 |
| 18 | 180222 |
| 19 | -339558 |
| 20 | 811374 |
| 21 | -2082534 |
| 22 | 4875774 |
| 23 | -10149702 |
| 24 | 22872750 |
| 25 | -55797126 |
| 26 | 133232766 |
| 27 | -294821286 |
| 28 | 660771438 |
| 29 | -1558556070 |
| 30 | 3711070590 |