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 | 3 |
| 2 | 13 |
| 3 | 61 |
| 4 | 251 |
| 5 | 1021 |
| 6 | 4093 |
| 7 | 16381 |
| 8 | 65521 |
| 9 | 262139 |
| 10 | 1048573 |
| 11 | 4194301 |
| 12 | 16777213 |
| 13 | 67108859 |
| 14 | 268435399 |
| 15 | 1073741789 |
| 16 | 4294967291 |
| 17 | 17179869143 |
| 18 | 68719476731 |
| 19 | 274877906899 |
| 20 | 1099511627689 |
| 21 | 4398046511093 |
| 22 | 17592186044399 |
| 23 | 70368744177643 |