362280

Appears in sequences

• a(0) = 1; a(n) = Sum_{k=1..n} (-1)^(k+1)*d(k+1)*a(n-k), where d() is the number of divisors (A000005).at n=22A307241
• Number of unoriented polyomino rings of length 2n with twofold rotational symmetry.at n=21A348402