cp's OEIS Frontend

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).

%I A249857 #12 Nov 12 2014 23:17:09
%S A249857 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 A249857 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 A249857 21,24,0,21,24,1,15,26,3,17,24,4,19,26,2,21,26
%N 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).
%C A249857 a(n) = A249777(n) - A249856(n).
%e A249857 .     |            |     unused even numbers <  A084937(n)    |
%e A249857 .   n | A084937(n) |     [uncounted odd terms in brackets]    | a(n)
%e A249857 . ----+------------+------------------------------------------+-----
%e A249857 .   3 |          3 |  _                                       |    0
%e A249857 .   4 |          5 |  4                                       |    1
%e A249857 .   5 |          4 |  _                                       |    0
%e A249857 .   6 |          7 |  6                                       |    1
%e A249857 .   7 |          9 |  6,8                                     |    2
%e A249857 .   8 |          8 |  6                                       |    1
%e A249857 .   9 |         11 |  6,10                                    |    2
%e A249857 .  10 |         13 |  6,10,12                                 |    3
%e A249857 .  11 |          6 |  _                                       |    0
%e A249857 .  12 |         17 |  10,12,14,[15],16                        |    4
%e A249857 .  13 |         19 |  10,12,14,[15],16,18                     |    5
%e A249857 .  14 |         10 |  _                                       |    0
%e A249857 .  15 |         21 |  12,14,[15],16,18,20                     |    5
%e A249857 .  16 |         23 |  12,14,[15],16,18,20,22                  |    6
%e A249857 .  17 |         16 |  12,14,[15]                              |    2
%e A249857 .  18 |         15 |  12,14                                   |    2
%e A249857 .  19 |         29 |  12,14,18,20,22,24,[25],26,[27],28       |    8
%e A249857 .  20 |         14 |  12                                      |    1
%e A249857 .  21 |         25 |  12,18,20,22,24                          |    5
%e A249857 .  22 |         27 |  12,18,20,22,24,26                       |    6
%e A249857 .  23 |         22 |  12,18,20                                |    3
%e A249857 .  24 |         31 |  12,18,20,24,26,28,30                    |    7
%e A249857 .  25 |         35 |  12,18,20,24,26,28,30,32,[33],34         |    9 .
%o A249857 (Haskell)
%o A249857 a249857 = sum . map ((1 -) . flip mod 2) . (uss !!)
%o A249857 -- See A249856 for definition of uss.
%Y A249857 Cf. A084937, A249777, A249856, A249858.
%Y A249857 For a different way to look at the missing numbers in A084937, see A249686, A250099, A250100.
%K A249857 nonn
%O A249857 1,7
%A A249857 _Reinhard Zumkeller_, Nov 09 2014