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 | 4 |
| 2 | 13 |
| 3 | 42 |
| 4 | 141 |
| 5 | 486 |
| 6 | 1685 |
| 7 | 5804 |
| 8 | 19769 |
| 9 | 66544 |
| 10 | 221581 |
| 11 | 730918 |
| 12 | 2391717 |
| 13 | 7772610 |
| 14 | 25110933 |
| 15 | 80713016 |
| 16 | 258280817 |
| 17 | 823269116 |
| 18 | 2615088973 |
| 19 | 8281113730 |
| 20 | 26150883901 |
| 21 | 82375282494 |
| 22 | 258893742933 |
| 23 | 811984918692 |
| 24 | 2541865829801 |
| 25 | 7943330715176 |