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 | 3 |
| 3 | 3 |
| 4 | -39 |
| 5 | -775 |
| 6 | -9045 |
| 7 | -85813 |
| 8 | -426447 |
| 9 | 7321329 |
| 10 | 325555155 |
| 11 | 7786757011 |
| 12 | 137053423881 |
| 13 | 1388713844713 |
| 14 | -21121997539461 |
| 15 | -1827406866674085 |
| 16 | -69034283067822495 |
| 17 | -1852635543265039903 |
| 18 | -30574875232261547613 |
| 19 | 308376017794648053539 |
| 20 | 54871741689019890859065 |