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%I #12 Nov 12 2014 23:17:09
%S 0,0,0,1,0,1,2,1,2,3,0,4,5,0,5,6,2,2,8,1,5,6,3,7,9,0,9,11,0,11,13,0,5,
%T 13,1,10,14,1,6,14,2,11,15,4,15,16,2,16,12,5,16,17,3,17,18,0,19,20,0,
%U 21,24,0,21,24,1,15,26,3,17,24,4,19,26,2,21,26
%N Let z = A084937: a(n) = number of even numbers <= z(n) that are != z(k) for k=1..n-1 and not coprime to z(n-1) and z(n-2).
%C a(n) = A249777(n) - A249856(n).
%e . | | unused even numbers < A084937(n) |
%e . n | A084937(n) | [uncounted odd terms in brackets] | a(n)
%e . ----+------------+------------------------------------------+-----
%e . 3 | 3 | _ | 0
%e . 4 | 5 | 4 | 1
%e . 5 | 4 | _ | 0
%e . 6 | 7 | 6 | 1
%e . 7 | 9 | 6,8 | 2
%e . 8 | 8 | 6 | 1
%e . 9 | 11 | 6,10 | 2
%e . 10 | 13 | 6,10,12 | 3
%e . 11 | 6 | _ | 0
%e . 12 | 17 | 10,12,14,[15],16 | 4
%e . 13 | 19 | 10,12,14,[15],16,18 | 5
%e . 14 | 10 | _ | 0
%e . 15 | 21 | 12,14,[15],16,18,20 | 5
%e . 16 | 23 | 12,14,[15],16,18,20,22 | 6
%e . 17 | 16 | 12,14,[15] | 2
%e . 18 | 15 | 12,14 | 2
%e . 19 | 29 | 12,14,18,20,22,24,[25],26,[27],28 | 8
%e . 20 | 14 | 12 | 1
%e . 21 | 25 | 12,18,20,22,24 | 5
%e . 22 | 27 | 12,18,20,22,24,26 | 6
%e . 23 | 22 | 12,18,20 | 3
%e . 24 | 31 | 12,18,20,24,26,28,30 | 7
%e . 25 | 35 | 12,18,20,24,26,28,30,32,[33],34 | 9 .
%o (Haskell)
%o a249857 = sum . map ((1 -) . flip mod 2) . (uss !!)
%o -- See A249856 for definition of uss.
%Y Cf. A084937, A249777, A249856, A249858.
%Y For a different way to look at the missing numbers in A084937, see A249686, A250099, A250100.
%K nonn
%O 1,7
%A _Reinhard Zumkeller_, Nov 09 2014
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