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 | 1 |
| 2 | 8 |
| 3 | 60 |
| 4 | 456 |
| 5 | 3535 |
| 6 | 27888 |
| 7 | 223209 |
| 8 | 1807760 |
| 9 | 14784759 |
| 10 | 121909800 |
| 11 | 1012208340 |
| 12 | 8454274920 |
| 13 | 70975888425 |
| 14 | 598536562848 |
| 15 | 5067375370380 |
| 16 | 43052078886048 |
| 17 | 366911053809199 |
| 18 | 3135773892098520 |
| 19 | 26867522192372988 |
| 20 | 230731788606093720 |