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 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 1 |
| 7 | 3 |
| 8 | 27 |
| 9 | 171 |
| 10 | 1249 |
| 11 | 8389 |
| 12 | 56079 |
| 13 | 360430 |
| 14 | 2272601 |
| 15 | 14037552 |
| 16 | 85516454 |
| 17 | 514976658 |
| 18 | 3074986408 |
| 19 | 18239677629 |
| 20 | 107654219304 |
| 21 | 632996894928 |
| 22 | 3711499493421 |
| 23 | 21716765203045 |
| 24 | 126880009607690 |
| 25 | 740528525043982 |
| 26 | 4319138789721875 |
| 27 | 25181507049874027 |
| 28 | 146788327084831744 |