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 | 15 |
| 3 | 81 |
| 4 | 435 |
| 5 | 2313 |
| 6 | 12195 |
| 7 | 63801 |
| 8 | 331395 |
| 9 | 1710153 |
| 10 | 8775075 |
| 11 | 44808921 |
| 12 | 227890755 |
| 13 | 1155180393 |
| 14 | 5839846755 |
| 15 | 29458152441 |
| 16 | 148335904515 |
| 17 | 745888593033 |
| 18 | 3746364947235 |
| 19 | 18799770158361 |
| 20 | 94271405748675 |
| 21 | 472449569948073 |
| 22 | 2366624981836515 |
| 23 | 11850654345690681 |
| 24 | 59323452211439235 |