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 | 1 |
| 1 | 7 |
| 2 | 47 |
| 3 | 342 |
| 4 | 2754 |
| 5 | 24552 |
| 6 | 241128 |
| 7 | 2592720 |
| 8 | 30334320 |
| 9 | 383970240 |
| 10 | 5231113920 |
| 11 | 76349105280 |
| 12 | 1188825724800 |
| 13 | 19675048780800 |
| 14 | 344937224217600 |
| 15 | 6386713749964800 |
| 16 | 124548748102195200 |
| 17 | 2551797512248320000 |
| 18 | 54804198761303040000 |
| 19 | 1231237843834521600000 |