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 | 840 |
| 1 | 2040 |
| 2 | 4440 |
| 3 | 9240 |
| 4 | 25320 |
| 5 | 51000 |
| 6 | 117480 |
| 7 | 271320 |
| 8 | 765480 |
| 9 | 1531320 |
| 10 | 3721800 |
| 11 | 7817640 |
| 12 | 15635640 |
| 13 | 32899560 |
| 14 | 65799480 |
| 15 | 139098120 |
| 16 | 349027320 |
| 17 | 699333000 |
| 18 | 1597611000 |
| 19 | 3386944680 |
| 20 | 9543610200 |
| 21 | 20041583280 |