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 | 6 |
| 4 | 96 |
| 5 | 1200 |
| 6 | 14760 |
| 7 | 196560 |
| 8 | 2983680 |
| 9 | 52315200 |
| 10 | 1041465600 |
| 11 | 22912243200 |
| 12 | 545443113600 |
| 13 | 13887294220800 |
| 14 | 376188856243200 |
| 15 | 10816657377926400 |
| 16 | 329526966472704000 |
| 17 | 10612556870243328000 |
| 18 | 360307460991724646400 |
| 19 | 12857257599818926694400 |
| 20 | 480829913352068087808000 |