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 | -3 |
| 6 | 6 |
| 7 | -6 |
| 8 | 8 |
| 9 | -12 |
| 10 | 24 |
| 11 | 24 |
| 12 | -30 |
| 13 | 40 |
| 14 | -60 |
| 15 | 120 |
| 16 | -120 |
| 17 | 144 |
| 18 | -180 |
| 19 | 240 |
| 20 | -360 |
| 21 | 720 |
| 22 | 720 |
| 23 | -840 |
| 24 | 1008 |
| 25 | -1260 |
| 26 | 1680 |
| 27 | -2520 |
| 28 | 5040 |
| 29 | -5040 |
| 30 | 5760 |
| 31 | -6720 |
| 32 | 8064 |
| 33 | -10080 |
| 34 | 13440 |
| 35 | -20160 |
| 36 | 40320 |
| 37 | 40320 |
| 38 | -45360 |
| 39 | 51840 |
| 40 | -60480 |
| 41 | 72576 |
| 42 | -90720 |
| 43 | 120960 |
| 44 | -181440 |
| 45 | 362880 |
| 46 | -362880 |
| 47 | 403200 |
| 48 | -453600 |
| 49 | 518400 |
| 50 | -604800 |
| 51 | 725760 |
| 52 | -907200 |
| 53 | 1209600 |
| 54 | -1814400 |
| 55 | 3628800 |