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A249857
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).
7
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, 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, 21, 24, 0, 21, 24, 1, 15, 26, 3, 17, 24, 4, 19, 26, 2, 21, 26
OFFSET
1,7
COMMENTS
a(n) = A249777(n) - A249856(n).
EXAMPLE
. | | unused even numbers < A084937(n) |
. n | A084937(n) | [uncounted odd terms in brackets] | a(n)
. ----+------------+------------------------------------------+-----
. 3 | 3 | _ | 0
. 4 | 5 | 4 | 1
. 5 | 4 | _ | 0
. 6 | 7 | 6 | 1
. 7 | 9 | 6,8 | 2
. 8 | 8 | 6 | 1
. 9 | 11 | 6,10 | 2
. 10 | 13 | 6,10,12 | 3
. 11 | 6 | _ | 0
. 12 | 17 | 10,12,14,[15],16 | 4
. 13 | 19 | 10,12,14,[15],16,18 | 5
. 14 | 10 | _ | 0
. 15 | 21 | 12,14,[15],16,18,20 | 5
. 16 | 23 | 12,14,[15],16,18,20,22 | 6
. 17 | 16 | 12,14,[15] | 2
. 18 | 15 | 12,14 | 2
. 19 | 29 | 12,14,18,20,22,24,[25],26,[27],28 | 8
. 20 | 14 | 12 | 1
. 21 | 25 | 12,18,20,22,24 | 5
. 22 | 27 | 12,18,20,22,24,26 | 6
. 23 | 22 | 12,18,20 | 3
. 24 | 31 | 12,18,20,24,26,28,30 | 7
. 25 | 35 | 12,18,20,24,26,28,30,32,[33],34 | 9 .
PROG
(Haskell)
a249857 = sum . map ((1 -) . flip mod 2) . (uss !!)
-- See A249856 for definition of uss.
CROSSREFS
For a different way to look at the missing numbers in A084937, see A249686, A250099, A250100.
Sequence in context: A273516 A082501 A249858 * A317441 A249777 A289065
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Nov 09 2014
STATUS
approved