A249856 Let z = A084937: a(n) = number of odd numbers <= z(n) that are != z(k) for k=1..n-1 and not coprime to z(n-1) and z(n-2).

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 1, 0, 2, 0, 0, 0, 0, 0, 1, 0, 1, 2, 0, 2, 3, 0, 0, 2, 0, 1, 2, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 2, 4, 0, 2, 3, 0, 0, 4, 0, 0, 2, 0, 0, 2, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0

Offset: 1

Author

Reinhard Zumkeller, Nov 09 2014

Keywords

• nonn

Comments

a(n) = A249777(n) - A249857(n).

Crossrefs

Cf. A084937, A249777, A249857, A249858.

For a different way to look at the missing numbers in A084937, see A249686, A250099, A250100.

Programs

Haskell

a249856 = sum . map (flip mod 2) . (uss !!)
uss = [] : [] : [] : f 2 1 [3..] where
   f x y zs = g zs [] where
      g (v:vs) ws | gcd v y > 1 || gcd v x > 1 = g vs (v : ws)
                  | otherwise = ws : f v x (delete v zs)