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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 24 |
| 5 | 900 |
| 6 | 18030 |
| 7 | 276570 |
| 8 | 3680964 |
| 9 | 45065160 |
| 10 | 523292010 |
| 11 | 5859909990 |
| 12 | 63862084704 |
| 13 | 680829769620 |
| 14 | 7122705252390 |
| 15 | 73284607133010 |
| 16 | 742843170653244 |
| 17 | 7429450873589280 |
| 18 | 73416173732059170 |
| 19 | 717721593866613630 |
| 20 | 6949589106333898584 |
| 21 | 66721599431782204140 |