OFFSET

1,1

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

LINKS

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

FORMULA

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

EXAMPLE

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.

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 *)

PROG

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

CROSSREFS

KEYWORD

nonn

AUTHOR

Altug Alkan, Feb 07 2017

STATUS

approved