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) |
|---|---|
| 1 | 3 |
| 2 | -3 |
| 3 | 11 |
| 4 | -21 |
| 5 | 51 |
| 6 | -119 |
| 7 | 315 |
| 8 | -831 |
| 9 | 2195 |
| 10 | -5883 |
| 11 | 16107 |
| 12 | -44357 |
| 13 | 122643 |
| 14 | -341487 |
| 15 | 956635 |
| 16 | -2690841 |
| 17 | 7596483 |
| 18 | -21522347 |
| 19 | 61171659 |
| 20 | -174342165 |
| 21 | 498112275 |
| 22 | -1426403751 |
| 23 | 4093181691 |
| 24 | -11767920107 |
| 25 | 33891544419 |
| 26 | -97764009003 |
| 27 | 282429537947 |
| 28 | -817028472645 |
| 29 | 2366564736723 |
| 30 | -6863037262207 |