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 | 0 |
| 1 | -1 |
| 2 | 5 |
| 3 | -13 |
| 4 | 29 |
| 5 | -61 |
| 6 | 125 |
| 7 | -253 |
| 8 | 509 |
| 9 | -1021 |
| 10 | 2045 |
| 11 | -4093 |
| 12 | 8189 |
| 13 | -16381 |
| 14 | 32765 |
| 15 | -65533 |
| 16 | 131069 |
| 17 | -262141 |
| 18 | 524285 |
| 19 | -1048573 |
| 20 | 2097149 |
| 21 | -4194301 |
| 22 | 8388605 |
| 23 | -16777213 |
| 24 | 33554429 |
| 25 | -67108861 |
| 26 | 134217725 |
| 27 | -268435453 |
| 28 | 536870909 |
| 29 | -1073741821 |
| 30 | 2147483645 |
| 31 | -4294967293 |