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) |
|---|---|
| 4 | 0 |
| 5 | 2 |
| 6 | 6 |
| 7 | 20 |
| 8 | 68 |
| 9 | 228 |
| 10 | 754 |
| 11 | 2456 |
| 12 | 7884 |
| 13 | 24982 |
| 14 | 78282 |
| 15 | 242998 |
| 16 | 748364 |
| 17 | 2289584 |
| 18 | 6966346 |
| 19 | 21098366 |
| 20 | 63651808 |
| 21 | 191406976 |
| 22 | 573998990 |
| 23 | 1717334182 |
| 24 | 5127933348 |
| 25 | 15286303526 |
| 26 | 45503354154 |
| 27 | 135287179508 |
| 28 | 401809091392 |
| 29 | 1192336418386 |