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A121998 Table, n-th row gives numbers between 1 and n that have a common factor with n. 9
2, 3, 2, 4, 5, 2, 3, 4, 6, 7, 2, 4, 6, 8, 3, 6, 9, 2, 4, 5, 6, 8, 10, 11, 2, 3, 4, 6, 8, 9, 10, 12, 13, 2, 4, 6, 7, 8, 10, 12, 14, 3, 5, 6, 9, 10, 12, 15, 2, 4, 6, 8, 10, 12, 14, 16, 17, 2, 3, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 19, 2, 4, 5, 6, 8, 10, 12, 14, 15, 16, 18, 20, 3, 6, 7, 9, 12, 14, 15 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

Row n contains numbers m <= n such that gcd(m,n) > 1, i.e., numbers m in the cototient of n. - Michael De Vlieger, Mar 13 2018

LINKS

Michael De Vlieger, Table of n, a(n) for n = 2..12949 (rows 2 <= n <= 256).

EXAMPLE

2;

3;

2,4;

5;

2,3,4,6;

7;

...

MATHEMATICA

Table[Select[Range@ n, ! CoprimeQ[#, n] &], {n, 20}] // Flatten (* Michael De Vlieger, Mar 13 2018 *)

CROSSREFS

Cf. A051953 (row lengths), A038566, A081520, A133995 (nondivisors in the cototient of n).

Sequence in context: A326764 A071495 A071515 * A120499 A027749 A226208

Adjacent sequences:  A121995 A121996 A121997 * A121999 A122000 A122001

KEYWORD

nonn,tabf

AUTHOR

Franklin T. Adams-Watters, Sep 11 2006

STATUS

approved

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Last modified June 6 10:33 EDT 2020. Contains 334842 sequences. (Running on oeis4.)