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 | 2 |
| 2 | 9 |
| 3 | 52 |
| 4 | 340 |
| 5 | 2394 |
| 6 | 17710 |
| 7 | 135720 |
| 8 | 1068012 |
| 9 | 8579560 |
| 10 | 70068713 |
| 11 | 580034052 |
| 12 | 4855986044 |
| 13 | 41043559340 |
| 14 | 349756577100 |
| 15 | 3001701610320 |
| 16 | 25921837477692 |
| 17 | 225083787458904 |
| 18 | 1963988670706228 |
| 19 | 17211860478150800 |
| 20 | 151433425446423120 |