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 | 10 |
| 4 | -1 |
| 5 | -280 |
| 6 | 56 |
| 7 | -1 |
| 8 | 15400 |
| 9 | -4620 |
| 10 | 126 |
| 11 | 120 |
| 12 | -1 |
| 13 | -1401400 |
| 14 | 560560 |
| 15 | -36036 |
| 16 | -17160 |
| 17 | 792 |
| 18 | 220 |
| 19 | -1 |
| 20 | 190590400 |
| 21 | -95295200 |
| 22 | 10090080 |
| 23 | 3203200 |
| 24 | -126126 |
| 25 | -360360 |
| 26 | -50050 |
| 27 | 1716 |
| 28 | 2002 |
| 29 | 364 |
| 30 | -1 |