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 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 14 |
| 6 | 50 |
| 7 | 202 |
| 8 | 872 |
| 9 | 4138 |
| 10 | 21132 |
| 11 | 115974 |
| 12 | 678514 |
| 13 | 4213596 |
| 14 | 27644234 |
| 15 | 190899306 |
| 16 | 1382957668 |
| 17 | 10480142146 |
| 18 | 82864865614 |
| 19 | 682076806158 |
| 20 | 5832742183906 |
| 21 | 51724158235168 |
| 22 | 474869816040776 |
| 23 | 4506715738447322 |