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) |
|---|---|
| 1 | 4 |
| 2 | 20 |
| 3 | 116 |
| 4 | 676 |
| 5 | 3940 |
| 6 | 22964 |
| 7 | 133844 |
| 8 | 780100 |
| 9 | 4546756 |
| 10 | 26500436 |
| 11 | 154455860 |
| 12 | 900234724 |
| 13 | 5246952484 |
| 14 | 30581480180 |
| 15 | 178241928596 |
| 16 | 1038870091396 |
| 17 | 6054978619780 |
| 18 | 35291001627284 |
| 19 | 205691031143924 |
| 20 | 1198855185236260 |