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 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 72 |
| 6 | 744 |
| 7 | 10416 |
| 8 | 270816 |
| 9 | 9906624 |
| 10 | 614210688 |
| 11 | 55278961920 |
| 12 | 8354817757440 |
| 13 | 1955027355240960 |
| 14 | 766650012876633600 |
| 15 | 478623425047744204800 |
| 16 | 492420437498707277414400 |
| 17 | 786887859122934229308211200 |
| 18 | 2148247421904894243053912064000 |