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 | 15 |
| 2 | 45 |
| 3 | 90 |
| 4 | 495 |
| 5 | 1866 |
| 6 | 5990 |
| 7 | 19920 |
| 8 | 62655 |
| 9 | 186525 |
| 10 | 526470 |
| 11 | 1403265 |
| 12 | 3530000 |
| 13 | 8388495 |
| 14 | 18884475 |
| 15 | 40442635 |
| 16 | 82775970 |
| 17 | 162663240 |
| 18 | 308201500 |
| 19 | 565176105 |
| 20 | 1006419120 |
| 21 | 1745321275 |
| 22 | 2955037455 |
| 23 | 4895398755 |
| 24 | 7950135835 |
| 25 | 12677752431 |