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 | 15 |
| 2 | 105 |
| 3 | 4950 |
| 4 | 33930 |
| 5 | 1594005 |
| 6 | 10925475 |
| 7 | 513264780 |
| 8 | 3517969140 |
| 9 | 165269665275 |
| 10 | 1132775137725 |
| 11 | 53216318953890 |
| 12 | 364750076378430 |
| 13 | 17135489433487425 |
| 14 | 117448391818716855 |
| 15 | 5517574381263997080 |
| 16 | 37818017415550449000 |
| 17 | 1776641815277573572455 |
| 18 | 12177284159415425861265 |