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 | 7 |
| 3 | 55 |
| 4 | 454 |
| 5 | 3850 |
| 6 | 33202 |
| 7 | 289606 |
| 8 | 2546773 |
| 9 | 22532905 |
| 10 | 200301403 |
| 11 | 1787165647 |
| 12 | 15993710992 |
| 13 | 143484404584 |
| 14 | 1289890360528 |
| 15 | 11615931435592 |
| 16 | 104760483639286 |
| 17 | 946005479787778 |
| 18 | 8552032916587066 |
| 19 | 77386316886280822 |
| 20 | 700854120680500744 |