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 | -2 |
| 4 | -1 |
| 5 | -2 |
| 6 | 18 |
| 7 | 68 |
| 8 | 311 |
| 9 | 1182 |
| 10 | 4370 |
| 11 | 15772 |
| 12 | 56754 |
| 13 | 203916 |
| 14 | 734636 |
| 15 | 2658096 |
| 16 | 9661591 |
| 17 | 35292134 |
| 18 | 129511602 |
| 19 | 477376556 |
| 20 | 1766730706 |
| 21 | 6563071700 |
| 22 | 24464139348 |
| 23 | 91478369336 |
| 24 | 343051112482 |
| 25 | 1289887370140 |
| 26 | 4861912443284 |
| 27 | 18367285959072 |
| 28 | 69533415236716 |
| 29 | 263747683314904 |
| 30 | 1002241674463968 |
| 31 | 3814985428350480 |
| 32 | 14544633872450487 |