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 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 0 |
| 9 | 40320 |
| 10 | 4032000 |
| 11 | 266112000 |
| 12 | 15008716800 |
| 13 | 794060467200 |
| 14 | 41179634496000 |
| 15 | 2142915046272000 |
| 16 | 113401428940800000 |
| 17 | 6150985123214131200 |
| 18 | 343578020565722342400 |
| 19 | 19818131438503157760000 |
| 20 | 1182304993642509574656000 |
| 21 | 73005714001076187082752000 |