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 | 1 |
| 3 | 3 |
| 4 | 0 |
| 5 | 205 |
| 6 | 0 |
| 7 | 39991 |
| 8 | 0 |
| 9 | 57 |
| 10 | 5905 |
| 11 | 9090909091 |
| 12 | 0 |
| 13 | 8230246567621 |
| 14 | 0 |
| 15 | 10371206370520815 |
| 16 | 0 |
| 17 | 17361641481138401521 |
| 18 | 0 |
| 19 | 37275544492386193492507 |
| 20 | 0 |
| 21 | 22706531343006 |
| 22 | 0 |
| 23 | 326583187044036098379401213863 |
| 24 | 0 |
| 25 | 45035996273705 |