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 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 12 |
| 6 | 60 |
| 7 | 378 |
| 8 | 3843 |
| 9 | 64455 |
| 10 | 1921532 |
| 11 | 104098702 |
| 12 | 10348794144 |
| 13 | 1893781768084 |
| 14 | 639954768875644 |
| 15 | 400905675004630820 |
| 16 | 467554784370658979194 |
| 17 | 1019317687720204607541914 |
| 18 | 4170177760438554428852944352 |
| 19 | 32130458453030025927403299167172 |