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 | 91 |
| 4 | 611 |
| 5 | 4368 |
| 6 | 32590 |
| 7 | 250821 |
| 8 | 1976441 |
| 9 | 15865465 |
| 10 | 129275835 |
| 11 | 1066438399 |
| 12 | 8888818659 |
| 13 | 74743312480 |
| 14 | 633272709348 |
| 15 | 5400983817990 |
| 16 | 46330852036920 |
| 17 | 399479717666693 |
| 18 | 3460229824525809 |
| 19 | 30095179524446946 |
| 20 | 262722158090170570 |
| 21 | 2301201197665717770 |