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 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 0 |
| 7 | -1 |
| 8 | 1 |
| 9 | 0 |
| 10 | -2 |
| 11 | 3 |
| 12 | 0 |
| 13 | -6 |
| 14 | 10 |
| 15 | 0 |
| 16 | -22 |
| 17 | 33 |
| 18 | 0 |
| 19 | -79 |
| 20 | 122 |
| 21 | 0 |
| 22 | -299 |
| 23 | 472 |
| 24 | 0 |
| 25 | -1179 |
| 26 | 1871 |
| 27 | 0 |
| 28 | -4754 |
| 29 | 7601 |
| 30 | 0 |
| 31 | -19553 |
| 32 | 31449 |
| 33 | 0 |
| 34 | -81720 |
| 35 | 132020 |
| 36 | 0 |
| 37 | -345949 |
| 38 | 561034 |
| 39 | 0 |
| 40 | -1480475 |
| 41 | 2408712 |
| 42 | 0 |
| 43 | -6394189 |
| 44 | 10431950 |
| 45 | 0 |
| 46 | -27835400 |
| 47 | 45521500 |
| 48 | 0 |
| 49 | -122008360 |
| 50 | 199948108 |
| 51 | 0 |
| 52 | -538016031 |
| 53 | 883331845 |
| 54 | 0 |