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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 9 |
| 5 | 27 |
| 6 | 63 |
| 7 | 126 |
| 8 | 252 |
| 9 | 504 |
| 10 | 1017 |
| 11 | 2043 |
| 12 | 4095 |
| 13 | 8190 |
| 14 | 16380 |
| 15 | 32760 |
| 16 | 65529 |
| 17 | 131067 |
| 18 | 262143 |
| 19 | 524286 |
| 20 | 1048572 |
| 21 | 2097144 |
| 22 | 4194297 |
| 23 | 8388603 |
| 24 | 16777215 |
| 25 | 33554430 |
| 26 | 67108860 |
| 27 | 134217720 |
| 28 | 268435449 |
| 29 | 536870907 |
| 30 | 1073741823 |
| 31 | 2147483646 |