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 | 2 |
| 4 | 6 |
| 5 | 20 |
| 6 | 71 |
| 7 | 263 |
| 8 | 1005 |
| 9 | 3933 |
| 10 | 15684 |
| 11 | 63505 |
| 12 | 260390 |
| 13 | 1079019 |
| 14 | 4511700 |
| 15 | 19011521 |
| 16 | 80653480 |
| 17 | 344193353 |
| 18 | 1476589475 |
| 19 | 6364258163 |
| 20 | 27545933212 |
| 21 | 119676949397 |
| 22 | 521739175908 |
| 23 | 2281673067934 |
| 24 | 10006784399183 |
| 25 | 44002280467770 |
| 26 | 193957104163645 |
| 27 | 856853526774173 |