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 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 22 |
| 6 | 71 |
| 7 | 240 |
| 8 | 816 |
| 9 | 2752 |
| 10 | 9313 |
| 11 | 31514 |
| 12 | 106590 |
| 13 | 360606 |
| 14 | 1219935 |
| 15 | 4126960 |
| 16 | 13961456 |
| 17 | 47231280 |
| 18 | 159782161 |
| 19 | 540539330 |
| 20 | 1828631430 |
| 21 | 6186215574 |
| 22 | 20927817799 |
| 23 | 70798300288 |
| 24 | 239508933824 |
| 25 | 810252920400 |
| 26 | 2741065994769 |
| 27 | 9272959837818 |
| 28 | 31370198430718 |