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 | 1 |
| 2 | 3 |
| 3 | 19 |
| 4 | 168 |
| 5 | 1582 |
| 6 | 15546 |
| 7 | 157051 |
| 8 | 1625368 |
| 9 | 17159223 |
| 10 | 184277224 |
| 11 | 2008388660 |
| 12 | 22172275440 |
| 13 | 247558926150 |
| 14 | 2791793968821 |
| 15 | 31764451979736 |
| 16 | 364283594455091 |
| 17 | 4207485803818522 |
| 18 | 48908343969469479 |
| 19 | 571811846280602486 |
| 20 | 6720473048598172508 |
| 21 | 79363083519870386700 |