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 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 20 |
| 6 | 54 |
| 7 | 146 |
| 8 | 436 |
| 9 | 1372 |
| 10 | 4577 |
| 11 | 15971 |
| 12 | 58376 |
| 13 | 221876 |
| 14 | 876012 |
| 15 | 3583099 |
| 16 | 15159817 |
| 17 | 66248609 |
| 18 | 298678064 |
| 19 | 1387677971 |
| 20 | 6637246978 |
| 21 | 32648574416 |
| 22 | 165002122350 |
| 23 | 855937433641 |
| 24 | 4553114299140 |
| 25 | 24813471826280 |
| 26 | 138417885372373 |
| 27 | 789683693019999 |
| 28 | 4603838061688077 |