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 | 93 |
| 4 | 639 |
| 5 | 4653 |
| 6 | 35169 |
| 7 | 272835 |
| 8 | 2157759 |
| 9 | 17319837 |
| 10 | 140668065 |
| 11 | 1153462995 |
| 12 | 9533639025 |
| 13 | 79326566595 |
| 14 | 663835030335 |
| 15 | 5582724468093 |
| 16 | 47152425626559 |
| 17 | 399769750195965 |
| 18 | 3400775573443089 |
| 19 | 29016970072920387 |
| 20 | 248256043372999089 |