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 | 1 |
| 3 | 1 |
| 4 | -1 |
| 5 | -17 |
| 6 | -107 |
| 7 | -415 |
| 8 | 1231 |
| 9 | 56671 |
| 10 | 924365 |
| 11 | 11322001 |
| 12 | 97495687 |
| 13 | -78466897 |
| 14 | -31987213451 |
| 15 | -1073614991039 |
| 16 | -26754505127713 |
| 17 | -558657850929473 |
| 18 | -9259584394031075 |
| 19 | -70982644052430799 |
| 20 | 3334438016903221111 |
| 21 | 240585292388924690959 |
| 22 | 10679411902033402697861 |