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 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 0 |
| 9 | 0 |
| 10 | 0 |
| 11 | 0 |
| 12 | 2 |
| 13 | 352 |
| 14 | 24440 |
| 15 | 1019616 |
| 16 | 33461568 |
| 17 | 957913824 |
| 18 | 25415753280 |
| 19 | 649347224736 |
| 20 | 16370397635328 |
| 21 | 413619939152632 |