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 | 1 |
| 3 | 0 |
| 4 | -3 |
| 5 | -9 |
| 6 | -18 |
| 7 | -27 |
| 8 | -27 |
| 9 | 0 |
| 10 | 81 |
| 11 | 243 |
| 12 | 486 |
| 13 | 729 |
| 14 | 729 |
| 15 | 0 |
| 16 | -2187 |
| 17 | -6561 |
| 18 | -13122 |
| 19 | -19683 |
| 20 | -19683 |
| 21 | 0 |
| 22 | 59049 |
| 23 | 177147 |
| 24 | 354294 |
| 25 | 531441 |
| 26 | 531441 |
| 27 | 0 |
| 28 | -1594323 |
| 29 | -4782969 |
| 30 | -9565938 |
| 31 | -14348907 |
| 32 | -14348907 |
| 33 | 0 |
| 34 | 43046721 |
| 35 | 129140163 |
| 36 | 258280326 |
| 37 | 387420489 |
| 38 | 387420489 |