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 | 3 |
| 2 | 13 |
| 3 | 57 |
| 4 | 249 |
| 5 | 1087 |
| 6 | 4745 |
| 7 | 20713 |
| 8 | 90417 |
| 9 | 394691 |
| 10 | 1722917 |
| 11 | 7520929 |
| 12 | 32830585 |
| 13 | 143313055 |
| 14 | 625594449 |
| 15 | 2730863665 |
| 16 | 11920848033 |
| 17 | 52037243619 |
| 18 | 227154537661 |
| 19 | 991581805481 |
| 20 | 4328482658041 |
| 21 | 18894822411423 |
| 22 | 82480245888473 |
| 23 | 360045244866137 |
| 24 | 1571680309076689 |
| 25 | 6860746056673507 |