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 | 7 |
| 3 | 15 |
| 4 | 101 |
| 5 | 297 |
| 6 | 1255 |
| 7 | 4565 |
| 8 | 21637 |
| 9 | 44583 |
| 10 | 63261 |
| 11 | 329931 |
| 12 | 1121505 |
| 13 | 2679689 |
| 14 | 4697205 |
| 15 | 6185689 |
| 16 | 23338469 |
| 17 | 49995925 |
| 18 | 431149389 |
| 19 | 3913864295 |
| 20 | 13610949895 |
| 21 | 80630964769 |
| 22 | 362326859895 |
| 23 | 749474411781 |
| 24 | 2168627105469 |
| 25 | 3646072432125 |
| 26 | 10085065885767 |
| 27 | 27152408925615 |