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 | -7 |
| 2 | 63 |
| 3 | -455 |
| 4 | 3983 |
| 5 | -29463 |
| 6 | 252511 |
| 7 | -1902439 |
| 8 | 16043055 |
| 9 | -122579639 |
| 10 | 1020990719 |
| 11 | -7885450503 |
| 12 | 65060930767 |
| 13 | -506646158935 |
| 14 | 4150058281887 |
| 15 | -32522243182247 |
| 16 | 264925506967919 |
| 17 | -2086171125173751 |
| 18 | 16921999515377215 |