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 | -3 |
| 3 | 7 |
| 4 | 1 |
| 5 | -219 |
| 6 | 2581 |
| 7 | -22973 |
| 8 | 162177 |
| 9 | -554039 |
| 10 | -10506419 |
| 11 | 343049631 |
| 12 | -6846400703 |
| 13 | 113528248237 |
| 14 | -1609627861659 |
| 15 | 17371462450651 |
| 16 | -36066494745599 |
| 17 | -5681921495461743 |
| 18 | 243263898097515037 |
| 19 | -7398126521141652809 |
| 20 | 193119003246643917441 |
| 21 | -4476119490014676723659 |
| 22 | 89171014860669488040757 |