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) |
|---|---|
| 2 | 2 |
| 3 | 12 |
| 4 | 76 |
| 5 | 545 |
| 6 | 4422 |
| 7 | 40194 |
| 8 | 405072 |
| 9 | 4484808 |
| 10 | 54121680 |
| 11 | 707105520 |
| 12 | 9944043840 |
| 13 | 149769846720 |
| 14 | 2405254884480 |
| 15 | 41029304803200 |
| 16 | 740857462732800 |
| 17 | 14117363667993600 |
| 18 | 283111532808652800 |
| 19 | 5960312380873267200 |
| 20 | 131434781395405824000 |
| 21 | 3029635129259289600000 |