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 | 6 |
| 2 | 18 |
| 3 | 60 |
| 4 | 210 |
| 5 | 726 |
| 6 | 2448 |
| 7 | 8448 |
| 8 | 28818 |
| 9 | 98556 |
| 10 | 336618 |
| 11 | 1150320 |
| 12 | 3928944 |
| 13 | 13419204 |
| 14 | 45828192 |
| 15 | 156512220 |
| 16 | 534463698 |
| 17 | 1825120584 |
| 18 | 6232259412 |
| 19 | 21281168202 |
| 20 | 72666555570 |
| 21 | 248124503652 |
| 22 | 847224827676 |
| 23 | 2892836367066 |
| 24 | 9877456541376 |
| 25 | 33725891989626 |