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 | 511 |
| 3 | 144115188075855871 |
| 4 | 904625697166532776746648320380374280103671755200316906558262375061821325311 |