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 | 7 |
| 2 | 35 |
| 3 | 105 |
| 4 | 273 |
| 5 | 4095 |
| 6 | 38115 |
| 7 | 86625 |
| 8 | 540225 |
| 9 | 22444695 |
| 10 | 215417475 |
| 11 | 1819488825 |
| 12 | 18942548625 |
| 13 | 273922023375 |
| 14 | 9015078147075 |
| 15 | 69890980784625 |
| 16 | -152873391045375 |
| 17 | 34948775541054375 |
| 18 | 718624343013451875 |
| 19 | 6694758964203935625 |