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 | 0 |
| 2 | 6 |
| 3 | 18 |
| 4 | 72 |
| 5 | 216 |
| 6 | 702 |
| 7 | 2106 |
| 8 | 6480 |
| 9 | 19440 |
| 10 | 58806 |
| 11 | 176418 |
| 12 | 530712 |
| 13 | 1592136 |
| 14 | 4780782 |
| 15 | 14342346 |
| 16 | 43040160 |
| 17 | 129120480 |
| 18 | 387400806 |
| 19 | 1162202418 |
| 20 | 3486725352 |
| 21 | 10460176056 |
| 22 | 31380882462 |
| 23 | 94142647386 |
| 24 | 282429005040 |
| 25 | 847287015120 |
| 26 | 2541864234006 |
| 27 | 7625592702018 |
| 28 | 22876787671992 |