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 | 4 |
| 1 | 220 |
| 2 | 10500 |
| 3 | 535500 |
| 4 | 30870000 |
| 5 | 2044828800 |
| 6 | 156029328000 |
| 7 | 13673998800000 |
| 8 | 1369285948800000 |
| 9 | 155756276676000000 |
| 10 | 20005336176265440000 |
| 11 | 2884501462544301600000 |
| 12 | 464334381775424160000000 |
| 13 | 83021688624014300160000000 |
| 14 | 16408769917253890176000000000 |
| 15 | 3569104362241728159962112000000 |
| 16 | 850861011640079911341911040000000 |