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 | 1 |
| 2 | 6 |
| 3 | 30 |
| 4 | 137 |
| 5 | 588 |
| 6 | 2415 |
| 7 | 9600 |
| 8 | 37209 |
| 9 | 141336 |
| 10 | 528049 |
| 11 | 1945800 |
| 12 | 7086555 |
| 13 | 25550547 |
| 14 | 91319973 |
| 15 | 323890062 |
| 16 | 1140985116 |
| 17 | 3995155506 |
| 18 | 13913280006 |
| 19 | 48216776266 |
| 20 | 166355744244 |
| 21 | 571636515369 |
| 22 | 1957015021744 |
| 23 | 6677155551312 |