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 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 84 |
| 6 | 334 |
| 7 | 1368 |
| 8 | 5734 |
| 9 | 24480 |
| 10 | 106086 |
| 11 | 465462 |
| 12 | 2063658 |
| 13 | 9231084 |
| 14 | 41610162 |
| 15 | 188820726 |
| 16 | 861891478 |
| 17 | 3954732384 |
| 18 | 18230522422 |
| 19 | 84390187986 |
| 20 | 392120098258 |
| 21 | 1828220666844 |
| 22 | 8550445900442 |
| 23 | 40103716079436 |