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 | 1 |
| 2 | 4 |
| 3 | 18 |
| 4 | 85 |
| 5 | 413 |
| 6 | 2044 |
| 7 | 10248 |
| 8 | 51876 |
| 9 | 264550 |
| 10 | 1357070 |
| 11 | 6994780 |
| 12 | 36196706 |
| 13 | 187938842 |
| 14 | 978599560 |
| 15 | 5108177816 |
| 16 | 26721644973 |
| 17 | 140050505085 |
| 18 | 735254208670 |
| 19 | 3865837887450 |
| 20 | 20353393741065 |
| 21 | 107290306033845 |
| 22 | 566194674179160 |
| 23 | 2990958274811520 |
| 24 | 15814562990604300 |
| 25 | 83690040760923168 |