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) |
|---|---|
| 1 | 0 |
| 2 | 4 |
| 3 | 13 |
| 4 | 80 |
| 5 | 381 |
| 6 | 1970 |
| 7 | 9940 |
| 8 | 50495 |
| 9 | 255980 |
| 10 | 1298632 |
| 11 | 6586395 |
| 12 | 33407907 |
| 13 | 169448914 |
| 14 | 859472004 |
| 15 | 4359369001 |
| 16 | 22111382192 |
| 17 | 112152257687 |
| 18 | 568853184739 |
| 19 | 2885309153794 |
| 20 | 14634723355722 |
| 21 | 74229524701062 |
| 22 | 376503348140640 |