548012945975
domain: N
Appears in sequences
- Number of 2-element intersecting families (with not necessarily distinct sets) of an n-element set.at n=20A053154
- Weighted count of equivalence classes of words w of length n+1 over {a, b, c, d, A, *} having exactly n letters, exactly one *, an even number of lowercase a's, and weight (-1)^(A(w)), where A(w) is the number of uppercase letters A.at n=19A390529