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 | 0 |
| 1 | 5 |
| 2 | 27 |
| 3 | 119 |
| 4 | 495 |
| 5 | 2015 |
| 6 | 8127 |
| 7 | 32639 |
| 8 | 130815 |
| 9 | 523775 |
| 10 | 2096127 |
| 11 | 8386559 |
| 12 | 33550335 |
| 13 | 134209535 |
| 14 | 536854527 |
| 15 | 2147450879 |
| 16 | 8589869055 |
| 17 | 34359607295 |
| 18 | 137438691327 |
| 19 | 549755289599 |
| 20 | 2199022206975 |
| 21 | 8796090925055 |
| 22 | 35184367894527 |
| 23 | 140737479966719 |
| 24 | 562949936644095 |