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 | 2 |
| 3 | 4 |
| 4 | 12 |
| 5 | 30 |
| 6 | 80 |
| 7 | 208 |
| 8 | 546 |
| 9 | 1428 |
| 10 | 3740 |
| 11 | 9790 |
| 12 | 25632 |
| 13 | 67104 |
| 14 | 175682 |
| 15 | 459940 |
| 16 | 1204140 |
| 17 | 3152478 |
| 18 | 8253296 |
| 19 | 21607408 |
| 20 | 56568930 |
| 21 | 148099380 |
| 22 | 387729212 |
| 23 | 1015088254 |
| 24 | 2657535552 |
| 25 | 6957518400 |
| 26 | 18215019650 |
| 27 | 47687540548 |
| 28 | 124847601996 |
| 29 | 326855265438 |
| 30 | 855718194320 |