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 | -4 |
| 3 | 1 |
| 4 | -20 |
| 5 | 64 |
| 6 | 1 |
| 7 | -56 |
| 8 | 784 |
| 9 | -2304 |
| 10 | 1 |
| 11 | -120 |
| 12 | 4368 |
| 13 | -52480 |
| 14 | 147456 |
| 15 | 1 |
| 16 | -220 |
| 17 | 16368 |
| 18 | -489280 |
| 19 | 5395456 |
| 20 | -14745600 |
| 21 | 1 |
| 22 | -364 |
| 23 | 48048 |
| 24 | -2846272 |
| 25 | 75851776 |
| 26 | -791691264 |
| 27 | 2123366400 |
| 28 | 1 |
| 29 | -560 |
| 30 | 119392 |
| 31 | -12263680 |
| 32 | 633721088 |
| 33 | -15658639360 |
| 34 | 157294854144 |
| 35 | -416179814400 |
| 36 | 1 |
| 37 | -816 |
| 38 | 262752 |
| 39 | -42828032 |
| 40 | 3773223168 |
| 41 | -177891237888 |
| 42 | 4165906530304 |
| 43 | -40683662475264 |
| 44 | 106542032486400 |
| 45 | 1 |
| 46 | -1140 |
| 47 | 527136 |
| 48 | -127959680 |
| 49 | 17649505536 |
| 50 | -1400415544320 |
| 51 | 61802667606016 |
| 52 | -1390437378293760 |
| 53 | 13288048674471936 |
| 54 | -34519618525593600 |