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 | 4 |
| 4 | 25 |
| 5 | 187 |
| 6 | 1772 |
| 7 | 17880 |
| 8 | 191967 |
| 9 | 2141232 |
| 10 | 24640989 |
| 11 | 290610414 |
| 12 | 3498042924 |
| 13 | 42831369777 |
| 14 | 532148952720 |
| 15 | 6695274478834 |
| 16 | 85166167050949 |
| 17 | 1093843440166718 |
| 18 | 14169564589464986 |
| 19 | 184957445502335682 |
| 20 | 2430876839834279341 |
| 21 | 32147041999684759275 |
| 22 | 427520786795342624432 |