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) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | 1 |
| 4 | 5 |
| 5 | -21 |
| 6 | -399 |
| 7 | 869 |
| 8 | 39325 |
| 9 | -334477 |
| 10 | -28717403 |
| 11 | 59697183 |
| 12 | 8400372435 |
| 13 | -34429291905 |
| 14 | -7199255611995 |
| 15 | 14631594576045 |
| 16 | 4251206967062925 |
| 17 | -68787420596367165 |
| 18 | -26475975382085110035 |
| 19 | 53392138323683746235 |
| 20 | 26275374869163335461975 |
| 21 | -105772979046693606062363 |