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 | 5 |
| 5 | 2 |
| 6 | 409 |
| 7 | 163 |
| 8 | 6553 |
| 9 | 2621 |
| 10 | 857 |
| 11 | 419 |
| 12 | 1677721 |
| 13 | 71 |
| 14 | 43 |
| 15 | 107 |
| 16 | 4294967 |
| 17 | 171798691 |
| 18 | 6871947673 |
| 19 | 779069 |
| 20 | 511627 |
| 21 | 4398046511 |
| 22 | 18604441 |
| 23 | 703687441 |
| 24 | 28147497671 |
| 25 | 11258999 |
| 26 | 59962737049 |
| 27 | 180143985094819 |
| 28 | 759403792793 |