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 | 1 |
| 2 | 3 |
| 3 | 33 |
| 4 | 195 |
| 5 | 1763 |
| 6 | 15623 |
| 7 | 156257 |
| 8 | 1630947 |
| 9 | 17911299 |
| 10 | 203739015 |
| 11 | 2389928995 |
| 12 | 28749060871 |
| 13 | 353362388551 |
| 14 | 4424242664975 |
| 15 | 56290517376737 |
| 16 | 726355164976547 |
| 17 | 9490129871680355 |
| 18 | 125375330053632455 |
| 19 | 1672895457018337859 |
| 20 | 22522481793315373319 |
| 21 | 305695116823973096519 |