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 | 3 |
| 4 | 6 |
| 5 | 38 |
| 6 | 213 |
| 7 | 1479 |
| 8 | 11692 |
| 9 | 104364 |
| 10 | 1036809 |
| 11 | 11344859 |
| 12 | 135548466 |
| 13 | 1755739218 |
| 14 | 24504637741 |
| 15 | 366596136399 |
| 16 | 5852040379224 |
| 17 | 99283915922264 |
| 18 | 1783921946910417 |
| 19 | 33840669046326579 |
| 20 | 675849838112277598 |
| 21 | 14174636583759324798 |