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 | 20 |
| 3 | 212 |
| 4 | 1768 |
| 5 | 13672 |
| 6 | 102012 |
| 7 | 745404 |
| 8 | 5374160 |
| 9 | 38400464 |
| 10 | 272709604 |
| 11 | 1928498596 |
| 12 | 13597146552 |
| 13 | 95668307256 |
| 14 | 672119557196 |
| 15 | 4717043931788 |
| 16 | 33080342678944 |
| 17 | 231867574534048 |
| 18 | 1624598900644788 |
| 19 | 11379821699044980 |