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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 0 |
| 4 | 2 |
| 5 | 1 |
| 6 | -5 |
| 7 | 20 |
| 8 | -28 |
| 9 | -47 |
| 10 | 525 |
| 11 | -2056 |
| 12 | 3902 |
| 13 | 9633 |
| 14 | -129033 |
| 15 | 664364 |
| 16 | -1837904 |
| 17 | -2388687 |
| 18 | 67004697 |
| 19 | -478198544 |
| 20 | 1994889946 |
| 21 | -1669470783 |
| 22 | -56929813933 |
| 23 | 615188040196 |
| 24 | -3794477505572 |
| 25 | 12028579019537 |
| 26 | 50780206473221 |
| 27 | -1172949397924184 |
| 28 | 10766410530764118 |