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 | 0 |
| 3 | -2 |
| 4 | -6 |
| 5 | -14 |
| 6 | -30 |
| 7 | -62 |
| 8 | -126 |
| 9 | -254 |
| 10 | -510 |
| 11 | -1022 |
| 12 | -2046 |
| 13 | -4094 |
| 14 | -8190 |
| 15 | -16382 |
| 16 | -32766 |
| 17 | -65534 |
| 18 | -131070 |
| 19 | -262142 |
| 20 | -524286 |
| 21 | -1048574 |
| 22 | -2097150 |
| 23 | -4194302 |
| 24 | -8388606 |
| 25 | -16777214 |
| 26 | -33554430 |
| 27 | -67108862 |
| 28 | -134217726 |
| 29 | -268435454 |
| 30 | -536870910 |
| 31 | -1073741822 |
| 32 | -2147483646 |