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 | 1 |
| 3 | 7 |
| 4 | 49 |
| 5 | 241 |
| 6 | 1681 |
| 7 | 18481 |
| 8 | 192193 |
| 9 | 2028097 |
| 10 | 26854561 |
| 11 | 400419361 |
| 12 | 6074016961 |
| 13 | 100260498625 |
| 14 | 1847840462833 |
| 15 | 36061045391281 |
| 16 | 738757221740161 |
| 17 | 16244778936351361 |
| 18 | 380460397886975809 |
| 19 | 9341152506044172865 |
| 20 | 241084169507148900481 |
| 21 | 6559259107807215358081 |