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 | 2 |
| 3 | 5 |
| 4 | 15 |
| 5 | 45 |
| 6 | 147 |
| 7 | 484 |
| 8 | 1649 |
| 9 | 5698 |
| 10 | 20055 |
| 11 | 71373 |
| 12 | 256998 |
| 13 | 933458 |
| 14 | 3418160 |
| 15 | 12601291 |
| 16 | 46739440 |
| 17 | 174281272 |
| 18 | 652962532 |
| 19 | 2456802244 |
| 20 | 9279423954 |
| 21 | 35170693226 |
| 22 | 133726116806 |
| 23 | 509926989456 |
| 24 | 1949634581725 |
| 25 | 7472405641631 |
| 26 | 28704432909043 |
| 27 | 110496066015970 |