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 | 4 |
| 2 | -1 |
| 3 | 20 |
| 4 | -10 |
| 5 | 1 |
| 6 | 120 |
| 7 | -90 |
| 8 | 18 |
| 9 | -1 |
| 10 | 840 |
| 11 | -840 |
| 12 | 252 |
| 13 | -28 |
| 14 | 1 |
| 15 | 6720 |
| 16 | -8400 |
| 17 | 3360 |
| 18 | -560 |
| 19 | 40 |
| 20 | -1 |
| 21 | 60480 |
| 22 | -90720 |
| 23 | 45360 |
| 24 | -10080 |
| 25 | 1080 |
| 26 | -54 |
| 27 | 1 |
| 28 | 604800 |
| 29 | -1058400 |
| 30 | 635040 |
| 31 | -176400 |
| 32 | 25200 |
| 33 | -1890 |
| 34 | 70 |
| 35 | -1 |
| 36 | 6652800 |
| 37 | -13305600 |
| 38 | 9313920 |