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 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 16 |
| 5 | 80 |
| 6 | 480 |
| 7 | 3296 |
| 8 | 25152 |
| 9 | 209600 |
| 10 | 1884160 |
| 11 | 18110080 |
| 12 | 184898304 |
| 13 | 1994964736 |
| 14 | 22654449664 |
| 15 | 269855506944 |
| 16 | 3362350046208 |
| 17 | 43715434232832 |
| 18 | 591812683833344 |
| 19 | 8326660788725760 |
| 20 | 121550217508892672 |
| 21 | 1838089917983911936 |
| 22 | 28753297176215257088 |
| 23 | 464675647688625364992 |