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 | 1 |
| 2 | -3 |
| 3 | -9 |
| 4 | -18 |
| 5 | -81 |
| 6 | -189 |
| 7 | -729 |
| 8 | -2052 |
| 9 | -6480 |
| 10 | -19197 |
| 11 | -59049 |
| 12 | -175446 |
| 13 | -531441 |
| 14 | -1589949 |
| 15 | -4781511 |
| 16 | -14335704 |
| 17 | -43046721 |
| 18 | -129097152 |
| 19 | -387420489 |
| 20 | -1162141182 |
| 21 | -3486771279 |
| 22 | -10459998909 |
| 23 | -31381059609 |
| 24 | -94142073420 |
| 25 | -282429529920 |
| 26 | -847285420797 |
| 27 | -2541865710960 |
| 28 | -7625587899366 |
| 29 | -22876792454961 |
| 30 | -68630348286531 |