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 | -3 |
| 2 | -15 |
| 3 | -51 |
| 4 | -159 |
| 5 | -483 |
| 6 | -1455 |
| 7 | -4371 |
| 8 | -13119 |
| 9 | -39363 |
| 10 | -118095 |
| 11 | -354291 |
| 12 | -1062879 |
| 13 | -3188643 |
| 14 | -9565935 |
| 15 | -28697811 |
| 16 | -86093439 |
| 17 | -258280323 |
| 18 | -774840975 |
| 19 | -2324522931 |
| 20 | -6973568799 |
| 21 | -20920706403 |
| 22 | -62762119215 |
| 23 | -188286357651 |