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) |
|---|---|
| 3 | 0 |
| 4 | 1 |
| 5 | 5 |
| 6 | 25 |
| 7 | 133 |
| 8 | 859 |
| 9 | 5781 |
| 10 | 40923 |
| 11 | 313005 |
| 12 | 2541251 |
| 13 | 21725314 |
| 14 | 195840223 |
| 15 | 1855631053 |
| 16 | 18408258491 |
| 17 | 190764140901 |
| 18 | 2060930694871 |
| 19 | 23161639995126 |
| 20 | 270260975209117 |
| 21 | 3268719600517612 |
| 22 | 40914280736043141 |
| 23 | 529233440391510248 |
| 24 | 7065125832189189159 |
| 25 | 97221637266999732570 |