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 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 21 |
| 5 | 91 |
| 6 | 291291 |
| 7 | 17574557 |
| 8 | 1433685253 |
| 9 | 2819787 |
| 10 | 14870951705 |
| 11 | 124958680680282 |
| 12 | 3525784478869018946300814 |
| 13 | 27359333221 |