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 | 0 |
| 2 | 0 |
| 3 | 216 |
| 4 | 16280 |
| 5 | 335655 |
| 6 | 3587535 |
| 7 | 25421200 |
| 8 | 135459216 |
| 9 | 584760870 |
| 10 | 2145870870 |
| 11 | 6918983280 |
| 12 | 20073184560 |
| 13 | 53334782501 |
| 14 | 131555523645 |
| 15 | 304453955520 |
| 16 | 666698215360 |
| 17 | 1390977293580 |
| 18 | 2780695001196 |
| 19 | 5351537889480 |
| 20 | 9954554649480 |
| 21 | 17957698726275 |