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 | 20 |
| 2 | 108 |
| 3 | 606 |
| 4 | 3002 |
| 5 | 14398 |
| 6 | 66950 |
| 7 | 306022 |
| 8 | 1382638 |
| 9 | 6200520 |
| 10 | 27671244 |
| 11 | 123093664 |
| 12 | 546418140 |
| 13 | 2422183000 |
| 14 | 10727201704 |
| 15 | 47478696368 |
| 16 | 210055317910 |
| 17 | 929074602120 |
| 18 | 4108554199540 |
| 19 | 18166666165648 |
| 20 | 80320554722730 |
| 21 | 355103563888676 |