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 | 5 |
| 3 | 33 |
| 4 | 251 |
| 5 | 2073 |
| 6 | 18069 |
| 7 | 163600 |
| 8 | 1523731 |
| 9 | 14504988 |
| 10 | 140499307 |
| 11 | 1380322749 |
| 12 | 13721269995 |
| 13 | 137758098052 |
| 14 | 1394840743638 |
| 15 | 14227181658075 |
| 16 | 146048314214619 |
| 17 | 1507739540085350 |
| 18 | 15643456882376418 |
| 19 | 163036276218805231 |
| 20 | 1706021256401103673 |