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 | 3 |
| 2 | 1 |
| 3 | 6 |
| 4 | 0 |
| 5 | 21 |
| 6 | 0 |
| 7 | 95 |
| 8 | 0 |
| 9 | 445 |
| 10 | 0 |
| 11 | 2181 |
| 12 | 0 |
| 13 | 11496 |
| 14 | 0 |
| 15 | 59723 |
| 16 | 0 |
| 17 | 315949 |
| 18 | 0 |
| 19 | 1718494 |
| 20 | 0 |
| 21 | 9403664 |
| 22 | 0 |