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 | -3 |
| 2 | 7 |
| 3 | -15 |
| 4 | 89 |
| 5 | -63 |
| 6 | 121 |
| 7 | -255 |
| 8 | 3521 |
| 9 | -13119 |
| 10 | 18273 |
| 11 | -4095 |
| 12 | -40319 |
| 13 | -16383 |
| 14 | 425089 |
| 15 | -2676735 |
| 16 | 6141953 |
| 17 | -262143 |
| 18 | -22487551 |
| 19 | -1048575 |
| 20 | 173791233 |
| 21 | -356171775 |
| 22 | 176138241 |
| 23 | -16777215 |
| 24 | 2378907649 |
| 25 | -5430575103 |
| 26 | 3355336705 |
| 27 | -38913703935 |
| 28 | 164745740289 |
| 29 | -1073741823 |
| 30 | -770681831423 |
| 31 | -4294967295 |
| 32 | 4113638096897 |
| 33 | -3796520402943 |
| 34 | 1133869137921 |
| 35 | -38542231207935 |
| 36 | 87257121292289 |
| 37 | -274877906943 |