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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 45 |
| 6 | 171 |
| 7 | 651 |
| 8 | 2488 |
| 9 | 9540 |
| 10 | 36690 |
| 11 | 141482 |
| 12 | 546864 |
| 13 | 2118207 |
| 14 | 8219967 |
| 15 | 31952115 |
| 16 | 124389552 |
| 17 | 484908408 |
| 18 | 1892657934 |
| 19 | 7395597354 |
| 20 | 28928182440 |
| 21 | 113260606074 |
| 22 | 443827115886 |
| 23 | 1740592240638 |
| 24 | 6831289801872 |
| 25 | 26829201570600 |