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) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 36 |
| 5 | 320 |
| 6 | 3750 |
| 7 | 54432 |
| 8 | 941192 |
| 9 | 18874368 |
| 10 | 430467210 |
| 11 | 11000000000 |
| 12 | 311249095212 |
| 13 | 9659108818944 |
| 14 | 326173191714734 |
| 15 | 11905721598812160 |
| 16 | 467086816406250000 |
| 17 | 19599665578316398592 |
| 18 | 875901453762003632658 |
| 19 | 41532319635035234107392 |
| 20 | 2082547005958224830656820 |