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 | 4 |
| 3 | 30 |
| 4 | 324 |
| 5 | 4540 |
| 6 | 78060 |
| 7 | 1589448 |
| 8 | 37388400 |
| 9 | 997513200 |
| 10 | 29759790240 |
| 11 | 981669324240 |
| 12 | 35475203063520 |
| 13 | 1393746645107232 |
| 14 | 59147129937893088 |
| 15 | 2696314664384853120 |
| 16 | 131405475202661963520 |
| 17 | 6817779852438948837120 |
| 18 | 375193156508083422581760 |