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 | 15 |
| 3 | 87 |
| 4 | 503 |
| 5 | 2871 |
| 6 | 16311 |
| 7 | 92599 |
| 8 | 525751 |
| 9 | 2985399 |
| 10 | 16952759 |
| 11 | 96267703 |
| 12 | 546663863 |
| 13 | 3104271799 |
| 14 | 17627835831 |
| 15 | 100100959671 |
| 16 | 568430652855 |
| 17 | 3227875241399 |
| 18 | 18329726840247 |
| 19 | 104086701305271 |
| 20 | 591063984860599 |