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 | 31 |
| 2 | 1921 |
| 3 | 7380481 |
| 4 | 108942999582721 |
| 5 | 23737154316161495960243527681 |
| 6 | 1126904990058528673830897031906808442930637286502826475521 |