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 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 0 |
| 5 | 9 |
| 6 | 0 |
| 7 | 225 |
| 8 | 0 |
| 9 | 11025 |
| 10 | 0 |
| 11 | 893025 |
| 12 | 0 |
| 13 | 108056025 |
| 14 | 0 |
| 15 | 18261468225 |
| 16 | 0 |
| 17 | 4108830350625 |
| 18 | 0 |
| 19 | 1187451971330625 |
| 20 | 0 |
| 21 | 428670161650355625 |
| 22 | 0 |
| 23 | 189043541287806830625 |
| 24 | 0 |
| 25 | 100004033341249813400625 |
| 26 | 0 |
| 27 | 62502520838281133375390625 |
| 28 | 0 |
| 29 | 45564337691106946230659765625 |
| 30 | 0 |