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A176554 Numbers n such that concatenations of divisors of n are nonprime. 4

%I

%S 1,2,4,5,6,8,10,11,12,14,15,16,17,18,19,20,22,23,24,25,26,27,28,29,30,

%T 32,33,34,35,36,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,

%U 56,57,58,59,60,61,62,63,64,65,66,68,69,70,71,72,74,75,76,77,78,80,81

%N Numbers n such that concatenations of divisors of n are nonprime.

%C See A037278(n) = concatenation of divisors of n. See A176556 for corresponding values of concatenations. Complement of A176553(n) for n >= 2.

%e a(6) = 8: divisors of 8 are 1,2,4,8 and their concatenation 1248 is nonprime.

%K nonn,base

%O 1,2

%A _Jaroslav Krizek_, Apr 20 2010

%E Edited and extended by _Charles R Greathouse IV_, Apr 30 2010

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Last modified January 27 01:45 EST 2021. Contains 340443 sequences. (Running on oeis4.)