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 | 7 |
| 4 | 21 |
| 5 | 61 |
| 6 | 191 |
| 7 | 603 |
| 8 | 1961 |
| 9 | 6457 |
| 10 | 21595 |
| 11 | 72975 |
| 12 | 249085 |
| 13 | 857013 |
| 14 | 2970007 |
| 15 | 10356323 |
| 16 | 36311633 |
| 17 | 127937649 |
| 18 | 452738867 |
| 19 | 1608426647 |
| 20 | 5734534629 |
| 21 | 20511509549 |
| 22 | 73583105007 |
| 23 | 264687136235 |
| 24 | 954482676217 |
| 25 | 3449853902761 |
| 26 | 12495597328011 |
| 27 | 45349353908383 |