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 | 2 |
| 2 | 0 |
| 3 | 0 |
| 4 | 8 |
| 5 | 30 |
| 6 | 192 |
| 7 | 1344 |
| 8 | 10800 |
| 9 | 97434 |
| 10 | 976000 |
| 11 | 10749024 |
| 12 | 129103992 |
| 13 | 1679495350 |
| 14 | 23525384064 |
| 15 | 353028802560 |
| 16 | 5650370001120 |
| 17 | 96082828074162 |
| 18 | 1729886440780800 |
| 19 | 32874134679574208 |
| 20 | 657589108734075240 |
| 21 | 13811277748363437006 |
| 22 | 303884178002526338624 |