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 | 1 |
| 3 | 1 |
| 4 | -23 |
| 5 | -119 |
| 6 | -359 |
| 7 | 6721 |
| 8 | 78961 |
| 9 | 450577 |
| 10 | -7867439 |
| 11 | -160506719 |
| 12 | -1421049959 |
| 13 | 23995634521 |
| 14 | 745945175977 |
| 15 | 9197488067041 |
| 16 | -152057966904479 |
| 17 | -6667968305775839 |
| 18 | -107047941299543519 |
| 19 | 1740437689443523777 |
| 20 | 102311231044267813321 |
| 21 | 2043217889363061489961 |