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 | 0 |
| 2 | 0 |
| 3 | 10 |
| 4 | 15 |
| 5 | 168 |
| 6 | 1008 |
| 7 | 8244 |
| 8 | 73125 |
| 9 | 726440 |
| 10 | 7939008 |
| 11 | 94744494 |
| 12 | 1225760627 |
| 13 | 17088219120 |
| 14 | 255365758560 |
| 15 | 4072255216296 |
| 16 | 69021889788969 |
| 17 | 1239055874931312 |
| 18 | 23484788783212480 |
| 19 | 468656477004105810 |
| 20 | 9821896865573503095 |