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 | 7 |
| 2 | 28 |
| 3 | 140 |
| 4 | 658 |
| 5 | 3164 |
| 6 | 15106 |
| 7 | 72302 |
| 8 | 345775 |
| 9 | 1654092 |
| 10 | 7911970 |
| 11 | 37846314 |
| 12 | 181033035 |
| 13 | 865951710 |
| 14 | 4142180085 |
| 15 | 19813648817 |
| 16 | 94776329265 |
| 17 | 453351783116 |
| 18 | 2168556616440 |
| 19 | 10373043626906 |
| 20 | 49618272850056 |
| 21 | 237343357526002 |