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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 5 |
| 6 | 20 |
| 7 | 75 |
| 8 | 271 |
| 9 | 957 |
| 10 | 3337 |
| 11 | 11559 |
| 12 | 39896 |
| 13 | 137423 |
| 14 | 472808 |
| 15 | 1625632 |
| 16 | 5587228 |
| 17 | 19198971 |
| 18 | 65963978 |
| 19 | 226623902 |
| 20 | 778551761 |
| 21 | 2674604282 |
| 22 | 9188106871 |
| 23 | 31563807424 |
| 24 | 108430368827 |
| 25 | 372487292867 |
| 26 | 1279591674070 |
| 27 | 4395730089428 |