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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 2 |
| 5 | 15 |
| 6 | 7 |
| 7 | 255 |
| 8 | 5 |
| 9 | 6 |
| 10 | 31 |
| 11 | 65535 |
| 12 | 11 |
| 13 | 4294967295 |
| 14 | 511 |
| 15 | 63 |
| 16 | 4 |
| 17 | 18446744073709551615 |
| 18 | 13 |
| 19 | 340282366920938463463374607431768211455 |
| 20 | 47 |
| 21 | 1023 |
| 22 | 131071 |
| 23 | 115792089237316195423570985008687907853269984665640564039457584007913129639935 |
| 24 | 23 |
| 25 | 30 |
| 26 | 8589934591 |
| 27 | 27 |
| 28 | 767 |