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 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 48 |
| 5 | 500 |
| 6 | 6480 |
| 7 | 100842 |
| 8 | 1835008 |
| 9 | 38263752 |
| 10 | 900000000 |
| 11 | 23579476910 |
| 12 | 681091006464 |
| 13 | 21505924728444 |
| 14 | 737020860878848 |
| 15 | 27246730957031250 |
| 16 | 1080863910568919040 |
| 17 | 45798768824157052688 |
| 18 | 2064472028642102280192 |
| 19 | 98646963440126439346902 |
| 20 | 4980736000000000000000000 |