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 | 0 |
| 2 | 1 |
| 3 | -1 |
| 4 | 8 |
| 5 | -12 |
| 6 | 65 |
| 7 | -125 |
| 8 | 544 |
| 9 | -1224 |
| 10 | 4657 |
| 11 | -11593 |
| 12 | 40520 |
| 13 | -107700 |
| 14 | 356561 |
| 15 | -988901 |
| 16 | 3161728 |
| 17 | -9014352 |
| 18 | 28179745 |
| 19 | -81795025 |
| 20 | 252010184 |
| 21 | -740036124 |
| 22 | 2258722337 |
| 23 | -6682944653 |
| 24 | 20273892640 |
| 25 | -60278338200 |
| 26 | 182146752721 |
| 27 | -543273442201 |
| 28 | 1637465696648 |
| 29 | -4893939533892 |
| 30 | 14726379083825 |