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 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 72 |
| 5 | 534 |
| 6 | 4818 |
| 7 | 50532 |
| 8 | 606408 |
| 9 | 8182656 |
| 10 | 122712912 |
| 11 | 2024328096 |
| 12 | 36432644400 |
| 13 | 710346495312 |
| 14 | 14915647605168 |
| 15 | 335567743462944 |
| 16 | 8052843408926976 |
| 17 | 205328108580310656 |
| 18 | 5543345188496499840 |
| 19 | 157970863597032124416 |
| 20 | 4738694884696030305024 |