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 | 4 |
| 2 | 31 |
| 3 | 244 |
| 4 | 1921 |
| 5 | 15124 |
| 6 | 119071 |
| 7 | 937444 |
| 8 | 7380481 |
| 9 | 58106404 |
| 10 | 457470751 |
| 11 | 3601659604 |
| 12 | 28355806081 |
| 13 | 223244789044 |
| 14 | 1757602506271 |
| 15 | 13837575261124 |
| 16 | 108942999582721 |
| 17 | 857706421400644 |
| 18 | 6752708371622431 |
| 19 | 53163960551578804 |