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 | 6 |
| 3 | 72 |
| 4 | 342 |
| 5 | 3330 |
| 6 | 36720 |
| 7 | 366660 |
| 8 | 4974480 |
| 9 | 67178160 |
| 10 | 1043189280 |
| 11 | 16836906240 |
| 12 | 303306806880 |
| 13 | 5705780240160 |
| 14 | 114832957599360 |
| 15 | 2475901844095680 |
| 16 | 55754442891987840 |
| 17 | 1331875774475326080 |
| 18 | 33292197644365820160 |