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 | 0 |
| 1 | 6 |
| 2 | 12 |
| 3 | 36 |
| 4 | 144 |
| 5 | 720 |
| 6 | 4320 |
| 7 | 30240 |
| 8 | 241920 |
| 9 | 2177280 |
| 10 | 21772800 |
| 11 | 239500800 |
| 12 | 2874009600 |
| 13 | 37362124800 |
| 14 | 523069747200 |
| 15 | 7846046208000 |
| 16 | 125536739328000 |
| 17 | 2134124568576000 |
| 18 | 38414242234368000 |
| 19 | 729870602452992000 |
| 20 | 14597412049059840000 |
| 21 | 306545653030256640000 |