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 | 6 |
| 2 | -18 |
| 3 | 144 |
| 4 | -1026 |
| 5 | 10368 |
| 6 | -91044 |
| 7 | 995328 |
| 8 | -9630090 |
| 9 | 109486080 |
| 10 | -1120744188 |
| 11 | 13042778112 |
| 12 | -138540597588 |
| 13 | 1637370298368 |
| 14 | -17853248637000 |
| 15 | 213325958873088 |
| 16 | -2371846639850586 |
| 17 | 28573129903177728 |
| 18 | -322526246042905740 |
| 19 | 3910007249908531200 |
| 20 | -44670671340291807228 |