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 | 11 |
| 2 | 15 |
| 3 | 39 |
| 4 | 135 |
| 5 | 2055 |
| 6 | 8199 |
| 7 | 131079 |
| 8 | 524295 |
| 9 | 8388615 |
| 10 | 536870919 |
| 11 | 2147483655 |
| 12 | 137438953479 |
| 13 | 2199023255559 |
| 14 | 8796093022215 |
| 15 | 140737488355335 |
| 16 | 9007199254740999 |
| 17 | 576460752303423495 |
| 18 | 2305843009213693959 |
| 19 | 147573952589676412935 |
| 20 | 2361183241434822606855 |