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 | -3 |
| 2 | 11 |
| 3 | 21 |
| 4 | -1313 |
| 5 | -595 |
| 6 | 90941 |
| 7 | 39109 |
| 8 | -5906513 |
| 9 | -4525731 |
| 10 | 1896204505 |
| 11 | 805349237 |
| 12 | -16784375281883 |
| 13 | -203564524787 |
| 14 | 10883940836027 |
| 15 | 69292329479205 |
| 16 | -359945426667971521 |
| 17 | -30553447357629763 |
| 18 | 279390122477674946807 |
| 19 | 16939595863125337813 |