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 | 4 |
| 2 | 1 |
| 3 | 15 |
| 4 | 0 |
| 5 | 93 |
| 6 | 0 |
| 7 | 668 |
| 8 | 0 |
| 9 | 5172 |
| 10 | 0 |
| 11 | 42042 |
| 12 | 0 |
| 13 | 353701 |
| 14 | 0 |
| 15 | 3036643 |
| 16 | 0 |
| 17 | 27045226 |
| 18 | 0 |
| 19 | 239093865 |
| 20 | 0 |
| 21 | 2158090933 |
| 22 | 0 |
| 23 | 19742800564 |
| 24 | 0 |
| 25 | 180815391365 |
| 26 | 0 |