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 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 3 |
| 5 | 18 |
| 6 | 60 |
| 7 | 1200 |
| 8 | 10500 |
| 9 | 735000 |
| 10 | 18522000 |
| 11 | 4667544000 |
| 12 | 359400888000 |
| 13 | 332086420512000 |
| 14 | 81408613942656000 |
| 15 | 279394363051195392000 |
| 16 | 224737840779305293440000 |
| 17 | 2892376010829659126572800000 |
| 18 | 7812628980363223707442752000000 |
| 19 | 379850021025259936655866602240000000 |