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 | 15 |
| 5 | 99 |
| 6 | 781 |
| 7 | 7001 |
| 8 | 69253 |
| 9 | 742071 |
| 10 | 8506775 |
| 11 | 103411463 |
| 12 | 1324477033 |
| 13 | 17785238513 |
| 14 | 249432247233 |
| 15 | 3642471258187 |
| 16 | 55246757713367 |
| 17 | 868523130653947 |
| 18 | 14127076257342933 |
| 19 | 237386074703124457 |
| 20 | 4115341407421082869 |
| 21 | 73516094755096807279 |
| 22 | 1351801707136238290351 |