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 | 25 |
| 5 | 121 |
| 6 | 1561 |
| 7 | 9871 |
| 8 | 101137 |
| 9 | 1293265 |
| 10 | 15765841 |
| 11 | 226501111 |
| 12 | 3355388521 |
| 13 | 55348183177 |
| 14 | 981791212585 |
| 15 | 19611613003711 |
| 16 | 387083895223201 |
| 17 | 8241127257050401 |
| 18 | 193814428658623777 |
| 19 | 4572332597344204135 |
| 20 | 116627907470591924281 |
| 21 | 3142752742361513926681 |