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 | -112 |
| 3 | -2123 |
| 4 | -16128 |
| 5 | -77101 |
| 6 | -275840 |
| 7 | -807159 |
| 8 | -2031616 |
| 9 | -4520825 |
| 10 | -8951424 |
| 11 | -15292867 |
| 12 | -19054592 |
| 13 | 4360347 |
| 14 | 163021952 |
| 15 | 902882449 |
| 16 | 4026531840 |
| 17 | 16769530511 |
| 18 | 68107256704 |
| 19 | 273984035205 |
| 20 | 1098231627776 |