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 | 1 |
| 1 | 1 |
| 2 | 7 |
| 3 | 53 |
| 4 | 511 |
| 5 | 6249 |
| 6 | 93311 |
| 7 | 1647085 |
| 8 | 33554431 |
| 9 | 774840977 |
| 10 | 19999999999 |
| 11 | 570623341221 |
| 12 | 17832200896511 |
| 13 | 605750213184505 |
| 14 | 22224013651116031 |
| 15 | 875787780761718749 |
| 16 | 36893488147419103231 |
| 17 | 1654480523772673528353 |
| 18 | 78692816150593075150847 |
| 19 | 3956839311320627178247957 |