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 | 0 |
| 2 | 4 |
| 3 | 6 |
| 4 | 12 |
| 5 | 30 |
| 6 | 70 |
| 7 | 168 |
| 8 | 412 |
| 9 | 1014 |
| 10 | 2514 |
| 11 | 6270 |
| 12 | 15702 |
| 13 | 39468 |
| 14 | 99516 |
| 15 | 251586 |
| 16 | 637500 |
| 17 | 1618638 |
| 18 | 4117102 |
| 19 | 10488684 |
| 20 | 26758762 |
| 21 | 68354250 |
| 22 | 174810354 |
| 23 | 447533586 |
| 24 | 1146836662 |
| 25 | 2941443180 |
| 26 | 7550434480 |
| 27 | 19395863358 |
| 28 | 49859516292 |
| 29 | 128252962434 |
| 30 | 330101861850 |