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 | 7 |
| 2 | 27 |
| 3 | 127 |
| 4 | 387 |
| 5 | 1935 |
| 6 | 6579 |
| 7 | 32767 |
| 8 | 98307 |
| 9 | 491535 |
| 10 | 1671219 |
| 11 | 8356095 |
| 12 | 25264899 |
| 13 | 126324495 |
| 14 | 429503283 |
| 15 | 2147483647 |
| 16 | 6442450947 |
| 17 | 32212254735 |
| 18 | 109521666099 |
| 19 | 547608330495 |
| 20 | 1655709893379 |
| 21 | 8278549466895 |
| 22 | 28147068187443 |
| 23 | 140735340937215 |
| 24 | 422218907713539 |