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) |
|---|---|
| 1 | 1 |
| 2 | -5 |
| 3 | 31 |
| 4 | -185 |
| 5 | 1111 |
| 6 | -6665 |
| 7 | 39991 |
| 8 | -239945 |
| 9 | 1439671 |
| 10 | -8638025 |
| 11 | 51828151 |
| 12 | -310968905 |
| 13 | 1865813431 |
| 14 | -11194880585 |
| 15 | 67169283511 |
| 16 | -403015701065 |
| 17 | 2418094206391 |
| 18 | -14508565238345 |
| 19 | 87051391430071 |
| 20 | -522308348580425 |
| 21 | 3133850091482551 |