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 | 3 |
| 2 | 13 |
| 3 | 63 |
| 4 | 309 |
| 5 | 1511 |
| 6 | 7373 |
| 7 | 35951 |
| 8 | 175269 |
| 9 | 854455 |
| 10 | 4165565 |
| 11 | 20307647 |
| 12 | 99002389 |
| 13 | 482649479 |
| 14 | 2352978861 |
| 15 | 11471077391 |
| 16 | 55922991237 |
| 17 | 272631840855 |
| 18 | 1329115610269 |
| 19 | 6479611111519 |
| 20 | 31588945184245 |
| 21 | 154000207833639 |