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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 9 |
| 5 | 112 |
| 6 | 1582 |
| 7 | 26159 |
| 8 | 486170 |
| 9 | 10131071 |
| 10 | 233582056 |
| 11 | 5895589738 |
| 12 | 161776346286 |
| 13 | 4794754890798 |
| 14 | 152576687930997 |
| 15 | 5187562649814737 |
| 16 | 187666786444911220 |
| 17 | 7196725552061993554 |
| 18 | 291572346138097726746 |
| 19 | 12443163766976461627878 |
| 20 | 557880276243757014820691 |