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 | 1 |
| 2 | 3 |
| 3 | 7 |
| 4 | 19 |
| 5 | 53 |
| 6 | 153 |
| 7 | 455 |
| 8 | 1359 |
| 9 | 4073 |
| 10 | 12213 |
| 11 | 36635 |
| 12 | 109899 |
| 13 | 329693 |
| 14 | 989073 |
| 15 | 2967215 |
| 16 | 8901639 |
| 17 | 26704913 |
| 18 | 80114733 |
| 19 | 240344195 |
| 20 | 721032579 |
| 21 | 2163097733 |
| 22 | 6489293193 |
| 23 | 19467879575 |
| 24 | 58403638719 |
| 25 | 175210916153 |
| 26 | 525632748453 |
| 27 | 1576898245355 |
| 28 | 4730694736059 |