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 | 5 |
| 2 | 15 |
| 3 | 85 |
| 4 | 215 |
| 5 | 1485 |
| 6 | 2815 |
| 7 | 26885 |
| 8 | 29415 |
| 9 | 508285 |
| 10 | 80015 |
| 11 | 10085685 |
| 12 | -8485385 |
| 13 | 210199085 |
| 14 | -379906785 |
| 15 | 4583888485 |
| 16 | -12182024185 |
| 17 | 103859793885 |
| 18 | -347500277585 |
| 19 | 2424696155285 |
| 20 | -9374701706985 |
| 21 | 57868624812685 |
| 22 | -245362658952385 |
| 23 | 1402735155206085 |
| 24 | -6309988334253785 |