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 | 2 |
| 2 | 4 |
| 3 | 26 |
| 4 | 106 |
| 5 | 1508 |
| 6 | 5860 |
| 7 | 221240 |
| 8 | -105080 |
| 9 | 68914880 |
| 10 | -673608800 |
| 11 | 40800296480 |
| 12 | -879775393760 |
| 13 | 40553067851840 |
| 14 | -1318206835981760 |
| 15 | 60190275180475520 |
| 16 | -2497504364769226880 |
| 17 | 122572211951306635520 |
| 18 | -6006028623693488806400 |
| 19 | 324246374847303660704000 |