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 | 9 |
| 3 | -27 |
| 4 | 63 |
| 5 | 117 |
| 6 | -4167 |
| 7 | 55953 |
| 8 | -651177 |
| 9 | 7336593 |
| 10 | -82438983 |
| 11 | 927666333 |
| 12 | -10331176977 |
| 13 | 110106505773 |
| 14 | -1023541502247 |
| 15 | 5304225184137 |
| 16 | 103363857534663 |
| 17 | -5240827920059127 |
| 18 | 158560193765332953 |
| 19 | -4192332947225516907 |
| 20 | 105290369454806352927 |