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 | 3 |
| 1 | 9 |
| 2 | 63 |
| 3 | 129 |
| 4 | 903 |
| 5 | 2193 |
| 6 | 15351 |
| 7 | 32769 |
| 8 | 229383 |
| 9 | 5577073 |
| 10 | 3899511 |
| 11 | 8421633 |
| 12 | 58951431 |
| 13 | 143167761 |
| 14 | 1002174327 |
| 15 | 2147483649 |
| 16 | 15032385543 |
| 17 | 36507222033 |
| 18 | 25550554231 |
| 19 | 551903297793 |
| 20 | 3863323084551 |
| 21 | 9382356062481 |
| 22 | 65676492437367 |
| 23 | 140739635904513 |
| 24 | 985177451331591 |
| 25 | 2392573810376721 |
| 26 | 16748016672637047 |
| 27 | 36170086427459841 |
| 28 | 25319060499221887 |
| 29 | 614891469266817297 |
| 30 | 4304240284867721079 |
| 31 | 9223372036854775809 |