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 | 3 |
| 1 | 13 |
| 2 | 69 |
| 3 | 415 |
| 4 | 2673 |
| 5 | 17863 |
| 6 | 121809 |
| 7 | 840055 |
| 8 | 5830593 |
| 9 | 40616263 |
| 10 | 283524849 |
| 11 | 1981523095 |
| 12 | 13858068513 |
| 13 | 96956127463 |
| 14 | 678491524689 |
| 15 | 4748635284535 |
| 16 | 33237225602433 |
| 17 | 232647693987463 |
| 18 | 1628482317649329 |
| 19 | 11399170063804375 |