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 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 6 |
| 6 | 456 |
| 7 | 6240 |
| 8 | 10936320 |
| 9 | 1225566720 |
| 10 | 130025295912960 |
| 11 | 252282619805368320 |
| 12 | 2209617218725251404267520 |
| 13 | 98758655816833727741338583040 |