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 | 1 |
| 3 | 9 |
| 4 | 65 |
| 5 | 442 |
| 6 | 2940 |
| 7 | 19380 |
| 8 | 127281 |
| 9 | 834900 |
| 10 | 5476185 |
| 11 | 35937525 |
| 12 | 236030652 |
| 13 | 1551652424 |
| 14 | 10210456360 |
| 15 | 67254204696 |
| 16 | 443410005585 |
| 17 | 2926078447656 |
| 18 | 19325957314755 |
| 19 | 127746785056275 |
| 20 | 845069382939705 |
| 21 | 5594334252541650 |