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 | 1 |
| 2 | 3 |
| 3 | 29 |
| 4 | 386 |
| 5 | 6774 |
| 6 | 146484 |
| 7 | 3762744 |
| 8 | 111868560 |
| 9 | 3777096240 |
| 10 | 142734788640 |
| 11 | 5967788097600 |
| 12 | 273488036169600 |
| 13 | 13631083378617600 |
| 14 | 734083968523046400 |
| 15 | 42477063883483622400 |
| 16 | 2628184745184816384000 |
| 17 | 173147202267665649408000 |
| 18 | 12100888735302910523904000 |
| 19 | 894183767796064712795136000 |