cp's OEIS Frontend

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).

%I A249856 #8 Nov 12 2014 23:16:21
%S A249856 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,
%T A249856 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,
%U A249856 0,2,0,0,2,0,0,1,0,0,1,0,0,0,0,0,0,0
%N 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).
%C A249856 a(n) = A249777(n) - A249857(n).
%o A249856 (Haskell)
%o A249856 a249856 = sum . map (flip mod 2) . (uss !!)
%o A249856 uss = [] : [] : [] : f 2 1 [3..] where
%o A249856    f x y zs = g zs [] where
%o A249856       g (v:vs) ws | gcd v y > 1 || gcd v x > 1 = g vs (v : ws)
%o A249856                   | otherwise = ws : f v x (delete v zs)
%Y A249856 Cf. A084937, A249777, A249857, A249858.
%Y A249856 For a different way to look at the missing numbers in A084937, see A249686, A250099, A250100.
%K A249856 nonn
%O A249856 1,19
%A A249856 _Reinhard Zumkeller_, Nov 09 2014