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 | 0 |
| 2 | -3 |
| 3 | 9 |
| 4 | -15 |
| 5 | 15 |
| 6 | -63 |
| 7 | 399 |
| 8 | -255 |
| 9 | -7425 |
| 10 | -1023 |
| 11 | 355839 |
| 12 | -4095 |
| 13 | -22360065 |
| 14 | -16383 |
| 15 | 1903790079 |
| 16 | -65535 |
| 17 | -209865211905 |
| 18 | -262143 |
| 19 | 29088885637119 |
| 20 | -1048575 |
| 21 | -4951498051026945 |
| 22 | -4194303 |
| 23 | 1015423886515240959 |
| 24 | -16777215 |
| 25 | -246921480190174429185 |