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 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 2 |
| 6 | 10 |
| 7 | 35 |
| 8 | 185 |
| 9 | 1242 |
| 10 | 13929 |
| 11 | 292131 |
| 12 | 12344252 |
| 13 | 1032326141 |
| 14 | 166163019475 |
| 15 | 50671385831320 |
| 16 | 29105332577409883 |
| 17 | 31455744378606296280 |
| 18 | 64032559078724993894492 |
| 19 | 245999991257359808853560276 |
| 20 | 1787823917424909126688749033668 |
| 21 | 24639597815428343970034635549911427 |