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 | -1 |
| 2 | -2 |
| 3 | -3 |
| 4 | -13 |
| 5 | -65 |
| 6 | -447 |
| 7 | -3351 |
| 8 | -28544 |
| 9 | -269270 |
| 10 | -2795872 |
| 11 | -31689198 |
| 12 | -389581679 |
| 13 | -5165672203 |
| 14 | -73512910689 |
| 15 | -1117937393138 |
| 16 | -18096787251877 |
| 17 | -310743077434399 |
| 18 | -5642249024063207 |
| 19 | -108023468997424550 |
| 20 | -2175086628366359447 |
| 21 | -45952007357795606912 |