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 | 5 |
| 2 | 15 |
| 3 | 45 |
| 4 | 135 |
| 5 | 406 |
| 6 | 1217 |
| 7 | 3650 |
| 8 | 10959 |
| 9 | 32941 |
| 10 | 99044 |
| 11 | 297812 |
| 12 | 895494 |
| 13 | 2692703 |
| 14 | 8096855 |
| 15 | 24346869 |
| 16 | 73209872 |
| 17 | 220138513 |
| 18 | 661945308 |
| 19 | 1990435887 |
| 20 | 5985139586 |
| 21 | 17997009753 |
| 22 | 54116091662 |
| 23 | 162724331983 |
| 24 | 489303778636 |
| 25 | 1471311543936 |