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 | 0 |
| 1 | 3 |
| 2 | 11 |
| 3 | 31 |
| 4 | 79 |
| 5 | 191 |
| 6 | 447 |
| 7 | 1023 |
| 8 | 2303 |
| 9 | 5119 |
| 10 | 11263 |
| 11 | 24575 |
| 12 | 53247 |
| 13 | 114687 |
| 14 | 245759 |
| 15 | 524287 |
| 16 | 1114111 |
| 17 | 2359295 |
| 18 | 4980735 |
| 19 | 10485759 |
| 20 | 22020095 |
| 21 | 46137343 |
| 22 | 96468991 |
| 23 | 201326591 |
| 24 | 419430399 |
| 25 | 872415231 |
| 26 | 1811939327 |
| 27 | 3758096383 |
| 28 | 7784628223 |
| 29 | 16106127359 |
| 30 | 33285996543 |
| 31 | 68719476735 |