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) |
|---|---|
| 1 | 3 |
| 2 | 15 |
| 3 | 55 |
| 4 | 173 |
| 5 | 511 |
| 6 | 1451 |
| 7 | 4019 |
| 8 | 10937 |
| 9 | 29371 |
| 10 | 78055 |
| 11 | 205679 |
| 12 | 538149 |
| 13 | 1399607 |
| 14 | 3621315 |
| 15 | 9327723 |
| 16 | 23931633 |
| 17 | 61186163 |
| 18 | 155949119 |
| 19 | 396369831 |
| 20 | 1004904733 |
| 21 | 2541896559 |
| 22 | 6416348251 |
| 23 | 16165611043 |
| 24 | 40657256617 |
| 25 | 102090514731 |
| 26 | 255968753175 |
| 27 | 640899345631 |
| 28 | 1602640560533 |