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 | 4 |
| 1 | 9 |
| 2 | 19 |
| 3 | 39 |
| 4 | 79 |
| 5 | 159 |
| 6 | 319 |
| 7 | 639 |
| 8 | 1279 |
| 9 | 2559 |
| 10 | 5119 |
| 11 | 10239 |
| 12 | 20479 |
| 13 | 40959 |
| 14 | 81919 |
| 15 | 163839 |
| 16 | 327679 |
| 17 | 655359 |
| 18 | 1310719 |
| 19 | 2621439 |
| 20 | 5242879 |
| 21 | 10485759 |
| 22 | 20971519 |
| 23 | 41943039 |
| 24 | 83886079 |
| 25 | 167772159 |
| 26 | 335544319 |
| 27 | 671088639 |
| 28 | 1342177279 |
| 29 | 2684354559 |