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 | -513 |
| 3 | 19684 |
| 4 | -261633 |
| 5 | 1953126 |
| 6 | -10097892 |
| 7 | 40353608 |
| 8 | -133955073 |
| 9 | 387440173 |
| 10 | -1001953638 |
| 11 | 2357947692 |
| 12 | -5149983972 |
| 13 | 10604499374 |
| 14 | -20701400904 |
| 15 | 38445332184 |
| 16 | -68584996353 |
| 17 | 118587876498 |
| 18 | -198756808749 |
| 19 | 322687697780 |
| 20 | -511002214758 |