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 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 14 |
| 5 | 48 |
| 6 | 384 |
| 7 | 1308 |
| 8 | 40288 |
| 9 | 933848 |
| 10 | 21077680 |
| 11 | 75690016 |
| 12 | 5471262080 |
| 13 | 7964665440 |
| 14 | 54595767744 |
| 15 | 17948164982144 |
| 16 | 3454946386353664 |
| 17 | 5010658671663616 |
| 18 | 723456523262697984 |
| 19 | 950502767770273280 |
| 20 | 165679731871366906880 |
| 21 | 8443707247468681128448 |