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 | -1 |
| 3 | -3 |
| 4 | -1 |
| 5 | -7 |
| 6 | 3 |
| 7 | -19 |
| 8 | 23 |
| 9 | -63 |
| 10 | 107 |
| 11 | -235 |
| 12 | 447 |
| 13 | -919 |
| 14 | 1811 |
| 15 | -3651 |
| 16 | 7271 |
| 17 | -14575 |
| 18 | 29115 |
| 19 | -58267 |
| 20 | 116495 |
| 21 | -233031 |
| 22 | 466019 |
| 23 | -932083 |
| 24 | 1864119 |
| 25 | -3728287 |
| 26 | 7456523 |
| 27 | -14913099 |
| 28 | 29826143 |
| 29 | -59652343 |
| 30 | 119304627 |
| 31 | -238609315 |
| 32 | 477218567 |
| 33 | -954437199 |