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 | 6 |
| 5 | 24 |
| 6 | 120 |
| 7 | 720 |
| 8 | 5040 |
| 9 | 20160 |
| 10 | 120960 |
| 11 | 907200 |
| 12 | 7983360 |
| 13 | 79833600 |
| 14 | 889574400 |
| 15 | 10897286400 |
| 16 | 81729648000 |
| 17 | 871782912000 |
| 18 | 11115232128000 |
| 19 | 160059342643200 |
| 20 | 2534272925184000 |
| 21 | 43444678717440000 |
| 22 | 798295971432960000 |
| 23 | 8781255685762560000 |
| 24 | 134645920515025920000 |