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 | 0 |
| 1 | 1 |
| 2 | 21 |
| 3 | 58 |
| 4 | 149 |
| 5 | 566 |
| 6 | 1676 |
| 7 | 5482 |
| 8 | 18021 |
| 9 | 59665 |
| 10 | 199700 |
| 11 | 670517 |
| 12 | 2259384 |
| 13 | 7624878 |
| 14 | 25759564 |
| 15 | 87078065 |
| 16 | 294452965 |
| 17 | 995889190 |
| 18 | 3368616437 |
| 19 | 11395096538 |
| 20 | 38547768152 |
| 21 | 130403228310 |
| 22 | 441145535869 |
| 23 | 1492374662977 |
| 24 | 5048648849760 |
| 25 | 17079422831941 |
| 26 | 57779211419220 |
| 27 | 195465558240778 |