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 | 117 |
| 4 | 609 |
| 5 | 3093 |
| 6 | 15561 |
| 7 | 77997 |
| 8 | 390369 |
| 9 | 1952613 |
| 10 | 9764601 |
| 11 | 48826077 |
| 12 | 244136529 |
| 13 | 1220694933 |
| 14 | 6103499241 |
| 15 | 30517545357 |
| 16 | 152587825089 |
| 17 | 762939322053 |
| 18 | 3814697003481 |
| 19 | 19073485803837 |
| 20 | 95367430592049 |
| 21 | 476837156105973 |
| 22 | 2384185786821321 |
| 23 | 11920928946689517 |