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 | 1 |
| 1 | 4 |
| 2 | 13 |
| 3 | 43 |
| 4 | 145 |
| 5 | 497 |
| 6 | 1727 |
| 7 | 6071 |
| 8 | 21554 |
| 9 | 77180 |
| 10 | 278426 |
| 11 | 1010990 |
| 12 | 3692213 |
| 13 | 13553555 |
| 14 | 49981875 |
| 15 | 185082495 |
| 16 | 687923790 |
| 17 | 2565602160 |
| 18 | 9598056630 |
| 19 | 36008860650 |
| 20 | 135446603370 |
| 21 | 510706730274 |
| 22 | 1929930236790 |
| 23 | 7308166696118 |
| 24 | 27727426756580 |
| 25 | 105387411817352 |
| 26 | 401231661076148 |
| 27 | 1529970156473276 |
| 28 | 5842655231153741 |
| 29 | 22342874048993015 |