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A068919 Squarefree orders of non-Abelian groups. 2
6, 10, 14, 21, 22, 26, 30, 34, 38, 39, 42, 46, 55, 57, 58, 62, 66, 70, 74, 78, 82, 86, 93, 94, 102, 105, 106, 110, 111, 114, 118, 122, 129, 130, 134, 138, 142, 146, 154, 155, 158, 165, 166, 170, 174, 178, 182, 183, 186, 190, 194, 195, 201, 202, 203, 205, 206 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This set is the difference A005117 \ A003277, that is, the squarefree numbers that are not cyclic (A003277). - Jeppe Stig Nielsen, Sep 25 2017

LINKS

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

MATHEMATICA

Complement[Select[Range[206], SquareFreeQ[#] &],

Select[Range[206], FiniteGroupCount[#] == 1 &]] (* Geoffrey Critzer, Nov 28 2015 *)

PROG

(Haskell)

a068919 n = a068919_list !! (n-1)

a068919_list = filter ((== 1) . a008966) a056868_list

-- Reinhard Zumkeller, Jun 28 2013

(PARI) is(n)=issquarefree(n)&&gcd(n, eulerphi(n))!=1 \\ Jeppe Stig Nielsen, Sep 25 2017

CROSSREFS

Intersection of A060652 and A005117.

Cf. A064899.

Also intersection of A056868 and A005117. - Reinhard Zumkeller, Jun 28 2013

Cf. A008966.

Sequence in context: A315222 A315223 A239699 * A060650 A068198 A064899

Adjacent sequences:  A068916 A068917 A068918 * A068920 A068921 A068922

KEYWORD

nonn

AUTHOR

Sharon Sela (sharonsela(AT)hotmail.com), Mar 29 2002

STATUS

approved

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Last modified April 24 19:49 EDT 2019. Contains 322446 sequences. (Running on oeis4.)