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) |
|---|---|
| 0 | 0 |
| 1 | 3 |
| 2 | 42 |
| 3 | 390 |
| 4 | 2940 |
| 5 | 19530 |
| 6 | 119196 |
| 7 | 684684 |
| 8 | 3758040 |
| 9 | 19909890 |
| 10 | 102539580 |
| 11 | 516023508 |
| 12 | 2547314952 |
| 13 | 12371513700 |
| 14 | 59252218200 |
| 15 | 280374917400 |
| 16 | 1312759571760 |
| 17 | 6089545431090 |
| 18 | 28014942671100 |
| 19 | 127932182324100 |