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 | 13 |
| 2 | 61 |
| 3 | 253 |
| 4 | 1021 |
| 5 | 4093 |
| 6 | 16381 |
| 7 | 65533 |
| 8 | 262141 |
| 9 | 1048573 |
| 10 | 4194301 |
| 11 | 16777213 |
| 12 | 67108861 |
| 13 | 268435453 |
| 14 | 1073741821 |
| 15 | 4294967293 |
| 16 | 17179869181 |
| 17 | 68719476733 |
| 18 | 274877906941 |
| 19 | 1099511627773 |
| 20 | 4398046511101 |
| 21 | 17592186044413 |
| 22 | 70368744177661 |