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 | 3 |
| 2 | 18 |
| 3 | 162 |
| 4 | 1944 |
| 5 | 29160 |
| 6 | 524880 |
| 7 | 11022480 |
| 8 | 264539520 |
| 9 | 7142567040 |
| 10 | 214277011200 |
| 11 | 7071141369600 |
| 12 | 254561089305600 |
| 13 | 9927882482918400 |
| 14 | 416971064282572800 |
| 15 | 18763697892715776000 |
| 16 | 900657498850357248000 |
| 17 | 45933532441368219648000 |
| 18 | 2480410751833883860992000 |