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 | 24 |
| 5 | 116 |
| 6 | 634 |
| 7 | 3762 |
| 8 | 23638 |
| 9 | 154816 |
| 10 | 1046010 |
| 11 | 7239440 |
| 12 | 51069582 |
| 13 | 365879686 |
| 14 | 2654987356 |
| 15 | 19473381290 |
| 16 | 144138193538 |
| 17 | 1075285161294 |
| 18 | 8076634643892 |
| 19 | 61028985689976 |
| 20 | 463596673890280 |
| 21 | 3538275218777642 |