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 | 0 |
| 2 | 3 |
| 3 | 3 |
| 4 | 21 |
| 5 | 63 |
| 6 | 243 |
| 7 | 969 |
| 8 | 3657 |
| 9 | 12987 |
| 10 | 43959 |
| 11 | 143685 |
| 12 | 458109 |
| 13 | 1435047 |
| 14 | 4439451 |
| 15 | 13612257 |
| 16 | 41474577 |
| 17 | 125798643 |
| 18 | 380343519 |
| 19 | 1147320285 |
| 20 | 3455328261 |
| 21 | 10394294175 |
| 22 | 31242648963 |
| 23 | 93853773369 |
| 24 | 281825558361 |
| 25 | 846030320043 |
| 26 | 2539248584583 |
| 27 | 7620161669109 |