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A249777 Let z = A084937: a(n) = number of numbers <= z(n) that are != z(k) for k=1..n-1 and not coprime to z(n-1) and z(n-2). 8
0, 0, 0, 1, 0, 1, 2, 1, 2, 3, 0, 5, 6, 0, 6, 7, 3, 2, 10, 1, 5, 6, 3, 7, 10, 0, 10, 13, 0, 13, 16, 0, 5, 15, 1, 11, 16, 1, 6, 15, 2, 11, 16, 4, 16, 17, 2, 17, 12, 5, 16, 17, 3, 17, 18, 0, 20, 21, 0, 23, 28, 0, 23, 27, 1, 15, 30, 3, 17, 26, 4, 19, 28, 2, 21 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,7

COMMENTS

a(A249684(n)) = 0.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

EXAMPLE

.   n | A084937(n) |    unused numbers less than A084937(n)   | 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                      |    5

.  13 |         19 |  10, 12, 14, 15, 16, 18                  |    6

.  14 |         10 |  _                                       |    0

.  15 |         21 |  12, 14, 15, 16, 18, 20                  |    6

.  16 |         23 |  12, 14, 15, 16, 18, 20, 22              |    7

.  17 |         16 |  12, 14, 15                              |    3

.  18 |         15 |  12, 14                                  |    2

.  19 |         29 |  12, 14, 18, 20, 22, 24, 25, 26, 27, 28  |   10

.  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  |   10 .

PROG

(Haskell)

a249777 n = a249777_list !! (n-1)

a249777_list = 0 : 0 : f 2 1 [3..] where

   f x y zs = g zs 0 where

      g (u:us) w | gcd y u > 1 || gcd x u > 1 = g us (w + 1)

                 | otherwise = w : f u x (delete u zs)

CROSSREFS

Cf. A084937, A249684.

Sequence in context: A249858 A249857 A317441 * A289065 A132815 A167684

Adjacent sequences:  A249774 A249775 A249776 * A249778 A249779 A249780

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Nov 05 2014

STATUS

approved

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Last modified December 6 22:42 EST 2021. Contains 349567 sequences. (Running on oeis4.)