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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 11 |
| 5 | 44 |
| 6 | 189 |
| 7 | 850 |
| 8 | 3951 |
| 9 | 18832 |
| 10 | 91542 |
| 11 | 452075 |
| 12 | 2261753 |
| 13 | 11439372 |
| 14 | 58394014 |
| 15 | 300455892 |
| 16 | 1556636807 |
| 17 | 8113709916 |
| 18 | 42518000652 |
| 19 | 223868503324 |
| 20 | 1183764310960 |
| 21 | 6283573101960 |
| 22 | 33470346433605 |
| 23 | 178850415320010 |