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 | 2 |
| 5 | -6 |
| 6 | 6 |
| 7 | -6 |
| 8 | 22 |
| 9 | -36 |
| 10 | 24 |
| 11 | 24 |
| 12 | -100 |
| 13 | 210 |
| 14 | -240 |
| 15 | 120 |
| 16 | -120 |
| 17 | 548 |
| 18 | -1350 |
| 19 | 2040 |
| 20 | -1800 |
| 21 | 720 |
| 22 | 720 |
| 23 | -3528 |
| 24 | 9744 |
| 25 | -17640 |
| 26 | 21000 |
| 27 | -15120 |
| 28 | 5040 |
| 29 | -5040 |
| 30 | 26136 |
| 31 | -78792 |
| 32 | 162456 |
| 33 | -235200 |
| 34 | 231840 |
| 35 | -141120 |
| 36 | 40320 |
| 37 | 40320 |
| 38 | -219168 |
| 39 | 708744 |
| 40 | -1614816 |
| 41 | 2693880 |
| 42 | -3265920 |
| 43 | 2751840 |
| 44 | -1451520 |
| 45 | 362880 |