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 | 1 |
| 2 | 10 |
| 3 | 90 |
| 4 | 840 |
| 5 | 8400 |
| 6 | 90720 |
| 7 | 1058400 |
| 8 | 13305600 |
| 9 | 179625600 |
| 10 | 2594592000 |
| 11 | 39956716800 |
| 12 | 653837184000 |
| 13 | 11333177856000 |
| 14 | 207484333056000 |
| 15 | 4001483566080000 |
| 16 | 81096733605888000 |
| 17 | 1723305589125120000 |
| 18 | 38318206628782080000 |
| 19 | 889833909490606080000 |
| 20 | 21543347282404147200000 |