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) |
|---|---|
| 1 | -1 |
| 2 | -1 |
| 3 | 1 |
| 4 | 11 |
| 5 | 49 |
| 6 | 179 |
| 7 | 601 |
| 8 | 1931 |
| 9 | 6049 |
| 10 | 18659 |
| 11 | 57001 |
| 12 | 173051 |
| 13 | 523249 |
| 14 | 1577939 |
| 15 | 4750201 |
| 16 | 14283371 |
| 17 | 42915649 |
| 18 | 128878019 |
| 19 | 386896201 |
| 20 | 1161212891 |
| 21 | 3484687249 |
| 22 | 10456158899 |
| 23 | 31372671001 |
| 24 | 94126401611 |
| 25 | 282395982049 |
| 26 | 847221500579 |
| 27 | 2541731610601 |
| 28 | 7625329049531 |
| 29 | 22876255584049 |