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 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 3 |
| 6 | 17 |
| 7 | 104 |
| 8 | 740 |
| 9 | 6006 |
| 10 | 54717 |
| 11 | 553254 |
| 12 | 6147264 |
| 13 | 74450194 |
| 14 | 976124761 |
| 15 | 13774204959 |
| 16 | 208143541601 |
| 17 | 3353423725801 |
| 18 | 57380805974819 |
| 19 | 1039230152655058 |
| 20 | 19860842917407766 |
| 21 | 399423618672311730 |