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 | 2 |
| 3 | -4 |
| 4 | 9 |
| 5 | -17 |
| 6 | 34 |
| 7 | -68 |
| 8 | 137 |
| 9 | -273 |
| 10 | 546 |
| 11 | -1092 |
| 12 | 2185 |
| 13 | -4369 |
| 14 | 8738 |
| 15 | -17476 |
| 16 | 34953 |
| 17 | -69905 |
| 18 | 139810 |
| 19 | -279620 |
| 20 | 559241 |
| 21 | -1118481 |
| 22 | 2236962 |
| 23 | -4473924 |
| 24 | 8947849 |
| 25 | -17895697 |
| 26 | 35791394 |
| 27 | -71582788 |
| 28 | 143165577 |
| 29 | -286331153 |
| 30 | 572662306 |
| 31 | -1145324612 |
| 32 | 2290649225 |
| 33 | -4581298449 |
| 34 | 9162596898 |