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 | 9 |
| 2 | 65 |
| 3 | 457 |
| 4 | 3201 |
| 5 | 22409 |
| 6 | 156865 |
| 7 | 1098057 |
| 8 | 7686401 |
| 9 | 53804809 |
| 10 | 376633665 |
| 11 | 2636435657 |
| 12 | 18455049601 |
| 13 | 129185347209 |
| 14 | 904297430465 |
| 15 | 6330082013257 |
| 16 | 44310574092801 |
| 17 | 310174018649609 |
| 18 | 2171218130547265 |
| 19 | 15198526913830857 |
| 20 | 106389688396816001 |
| 21 | 744727818777712009 |