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 | 4 |
| 1 | 28 |
| 2 | 138 |
| 3 | 629 |
| 4 | 2784 |
| 5 | 12134 |
| 6 | 52366 |
| 7 | 224404 |
| 8 | 956514 |
| 9 | 4060036 |
| 10 | 17175130 |
| 11 | 72454073 |
| 12 | 304941384 |
| 13 | 1280898302 |
| 14 | 5371301502 |
| 15 | 22491017756 |
| 16 | 94055344242 |
| 17 | 392888085098 |
| 18 | 1639534704630 |
| 19 | 6835739258996 |
| 20 | 28477594607346 |
| 21 | 118551827347574 |