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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 10 |
| 5 | 25 |
| 6 | 72 |
| 7 | 182 |
| 8 | 502 |
| 9 | 1332 |
| 10 | 3720 |
| 11 | 10380 |
| 12 | 30142 |
| 13 | 88842 |
| 14 | 270569 |
| 15 | 842957 |
| 16 | 2703060 |
| 17 | 8885029 |
| 18 | 29990388 |
| 19 | 103743388 |
| 20 | 367811233 |
| 21 | 1334925589 |
| 22 | 4957151327 |
| 23 | 18817501736 |
| 24 | 72972267232 |
| 25 | 288863499000 |
| 26 | 1166486601571 |
| 27 | 4802115258807 |
| 28 | 20141268290050 |
| 29 | 86017885573548 |
| 30 | 373852868791639 |