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) |
|---|---|
| 2 | 1 |
| 3 | 4 |
| 4 | 13 |
| 5 | 41 |
| 6 | 131 |
| 7 | 428 |
| 8 | 1429 |
| 9 | 4861 |
| 10 | 16795 |
| 11 | 58785 |
| 12 | 208011 |
| 13 | 742899 |
| 14 | 2674439 |
| 15 | 9694844 |
| 16 | 35357669 |
| 17 | 129644789 |
| 18 | 477638699 |
| 19 | 1767263189 |
| 20 | 6564120419 |
| 21 | 24466267019 |
| 22 | 91482563639 |
| 23 | 343059613649 |
| 24 | 1289904147323 |
| 25 | 4861946401451 |
| 26 | 18367353072151 |
| 27 | 69533550916003 |
| 28 | 263747951750359 |