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 | 6 |
| 4 | 20 |
| 5 | 68 |
| 6 | 231 |
| 7 | 781 |
| 8 | 2629 |
| 9 | 8821 |
| 10 | 29530 |
| 11 | 98706 |
| 12 | 329592 |
| 13 | 1099792 |
| 14 | 3668127 |
| 15 | 12230505 |
| 16 | 40771337 |
| 17 | 135895689 |
| 18 | 452914658 |
| 19 | 1509385902 |
| 20 | 5029980252 |
| 21 | 16761785436 |
| 22 | 55855539047 |
| 23 | 186125915029 |
| 24 | 620217261197 |
| 25 | 2066704787645 |
| 26 | 6886704234970 |
| 27 | 22947920663130 |
| 28 | 76467083518464 |