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 | 3 |
| 2 | 12 |
| 3 | 39 |
| 4 | 138 |
| 5 | 426 |
| 6 | 1461 |
| 7 | 4458 |
| 8 | 14655 |
| 9 | 45309 |
| 10 | 145479 |
| 11 | 443037 |
| 12 | 1427196 |
| 13 | 4329696 |
| 14 | 13655325 |
| 15 | 41795679 |
| 16 | 131102229 |
| 17 | 397649811 |
| 18 | 1247247507 |
| 19 | 3775785681 |
| 20 | 11761535064 |
| 21 | 35770717695 |
| 22 | 110693177805 |
| 23 | 335003030301 |
| 24 | 1040296817955 |
| 25 | 3145674794979 |
| 26 | 9695067728493 |
| 27 | 29405519846121 |