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 | 2 |
| 2 | 15 |
| 3 | 112 |
| 4 | 879 |
| 5 | 7084 |
| 6 | 58123 |
| 7 | 482980 |
| 8 | 4051542 |
| 9 | 34236670 |
| 10 | 291001515 |
| 11 | 2485209984 |
| 12 | 21308128100 |
| 13 | 183304844334 |
| 14 | 1581390987039 |
| 15 | 13676468811804 |
| 16 | 118533903449357 |
| 17 | 1029280548493050 |
| 18 | 8952719328878815 |
| 19 | 77988115665259800 |
| 20 | 680280714418808610 |
| 21 | 5941248392350208706 |