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 | 1 |
| 2 | 6 |
| 3 | 50 |
| 4 | 490 |
| 5 | 5187 |
| 6 | 59080 |
| 7 | 675012 |
| 8 | 8723880 |
| 9 | 84841130 |
| 10 | 2106192682 |
| 11 | -26974249302 |
| 12 | 2765793096248 |
| 13 | -163142299607490 |
| 14 | 11813146551718560 |
| 15 | -906751607066476056 |
| 16 | 75382006693375808940 |
| 17 | -6718584345560312459292 |
| 18 | 639573513055226901933760 |
| 19 | -64760465046707144137421880 |
| 20 | 6950351671309757070230871462 |