A282160 Least k > 1 such that k*n is not a totient number.

3, 7, 3, 17, 3, 15, 2, 19, 3, 5, 3, 43, 2, 7, 3, 19, 2, 5, 2, 17, 3, 7, 3, 167, 2, 7, 3, 11, 3, 3, 2, 19, 3, 2, 3, 67, 2, 2, 3, 17, 3, 17, 2, 7, 2, 5, 2, 211, 2, 7, 3, 7, 3, 11, 3, 13, 2, 3, 2, 139, 2, 2, 3, 31, 3, 9, 2, 5, 3, 5, 2, 109, 2, 5, 3, 2, 2, 3, 2, 85, 3, 3, 3, 61

Offset: 1

Author

Altug Alkan, Feb 07 2017

Keywords

• nonn

Comments

First occurrence of odd k or zero if impossible: 0, 1, 10, 2, 66, 28, 56, 6, 4, 8, 5244, 460, 272, 0, 232, 64, 7788, 4180, 300, 348, 328, 12, etc. - Robert G. Wilson v, Feb 09 2017

Examples

			a(14) = 7 because 7 * 14 = 98 is not a totient number and 7 is the least number that is greater than 1 with this property.
		

Links

• Altug Alkan, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000010, A002202, A007617, A067005, A071615, A079695.

Programs

Mathematica

TotientQ[m_] := Select[ Range[m +1, 2m*Product[(1 - 1/(k*Log[k]))^(-1), {k, 2, DivisorSigma[0, m]}]], EulerPhi[#] == m &, 1] != {}; (* after Jean-François Alcover, May 23 2011 in A002202 *) f[n_] := Block[{k = 2}, While[ TotientQ[k*n], k++]; k]; Array[f, 84] (* Robert G. Wilson v, Feb 09 2017 *)

PARI

a(n) = my(k = 2); while (istotient(k*n), k++); k;

Formula

a(A079695(n)) = 2. - Michel Marcus, Feb 08 2017