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 | -5 |
| 3 | 15 |
| 4 | -565 |
| 5 | -7085 |
| 6 | 25575 |
| 7 | -1266205 |
| 8 | -17602325 |
| 9 | 941362695 |
| 10 | 197665011735 |
| 11 | 2901803883615 |
| 12 | -11147523830125 |
| 13 | -165269711096165 |
| 14 | 637677823344495 |
| 15 | 2154364271382137415 |
| 16 | -126774939137440139965 |
| 17 | -1925041114036033717685 |
| 18 | -447232673152232758272805 |
| 19 | -6839447730858454557453725 |
| 20 | 410508614063545790640124095 |
| 21 | -1608693655111966245554191885 |