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 | 3 |
| 2 | -1 |
| 3 | 24 |
| 4 | -125 |
| 5 | 924 |
| 6 | -6895 |
| 7 | 54181 |
| 8 | -438737 |
| 9 | 3639655 |
| 10 | -30769033 |
| 11 | 264122781 |
| 12 | -2296010693 |
| 13 | 20171456222 |
| 14 | -178818115155 |
| 15 | 1597550237324 |
| 16 | -14369097515939 |
| 17 | 130010781029079 |
| 18 | -1182520161325459 |
| 19 | 10806114831458755 |
| 20 | -99163805247182631 |
| 21 | 913441732959868748 |