A121998 Table, n-th row gives numbers between 1 and n that have a common factor with n.

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

Offset: 2

Author

Franklin T. Adams-Watters, Sep 11 2006

Keywords

• nonn
• tabf

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

Examples

			2;
3;
2,4;
5;
2,3,4,6;
7;
...
		

Links

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

Crossrefs

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

Programs

Mathematica

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