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 | 0 |
| 1 | 3 |
| 2 | 21 |
| 3 | 171 |
| 4 | 1365 |
| 5 | 10923 |
| 6 | 87381 |
| 7 | 699051 |
| 8 | 5592405 |
| 9 | 44739243 |
| 10 | 357913941 |
| 11 | 2863311531 |
| 12 | 22906492245 |
| 13 | 183251937963 |
| 14 | 1466015503701 |
| 15 | 11728124029611 |
| 16 | 93824992236885 |
| 17 | 750599937895083 |
| 18 | 6004799503160661 |
| 19 | 48038396025285291 |
| 20 | 384307168202282325 |
| 21 | 3074457345618258603 |