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 | 45 |
| 3 | 1260 |
| 4 | 51975 |
| 5 | 2837835 |
| 6 | 192972780 |
| 7 | 15713497800 |
| 8 | 1490818103775 |
| 9 | 161505294575625 |
| 10 | 19671344879311125 |
| 11 | 2660996470946814000 |
| 12 | 395823225053338582500 |
| 13 | 64214706279807005422500 |
| 14 | 11283441246308945238525000 |
| 15 | 2134827083801652439128930000 |