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 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 8 |
| 6 | 38 |
| 7 | 192 |
| 8 | 1320 |
| 9 | 10176 |
| 10 | 91296 |
| 11 | 908160 |
| 12 | 9985920 |
| 13 | 119761920 |
| 14 | 1556847360 |
| 15 | 21794734080 |
| 16 | 326920043520 |
| 17 | 5230700052480 |
| 18 | 88921882828800 |
| 19 | 1600593472880640 |
| 20 | 30411275613143040 |
| 21 | 608225502973132800 |