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 | 0 |
| 3 | 2 |
| 4 | -3 |
| 5 | -2 |
| 6 | 21 |
| 7 | -44 |
| 8 | -62 |
| 9 | 631 |
| 10 | -1367 |
| 11 | -3170 |
| 12 | 34849 |
| 13 | -86855 |
| 14 | -302964 |
| 15 | 3058342 |
| 16 | -8509971 |
| 17 | -36488802 |
| 18 | 430842051 |
| 19 | -1111575888 |
| 20 | -6244999438 |
| 21 | 78663444549 |
| 22 | -250850311489 |
| 23 | -1724880111306 |
| 24 | 18475299723737 |
| 25 | -65061274823853 |
| 26 | -444914618968648 |
| 27 | 6831921081061986 |