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 | 23 |
| 4 | 119 |
| 5 | 1119 |
| 6 | 19259 |
| 7 | 417143 |
| 8 | 10567983 |
| 9 | 309715199 |
| 10 | 10335277619 |
| 11 | 386840046999 |
| 12 | 16045111426343 |
| 13 | 730346987476703 |
| 14 | 36191354975508459 |
| 15 | 1939288175212058999 |
| 16 | 111724538084900577119 |
| 17 | 6886112439566787983103 |
| 18 | 452112545350650426838883 |