Search: id:A068014
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%I A068014
%S A068014 6,10,14,21,26,34,38,40,46,55,57,58,60,63,74,76,86,88,93,111,114,117,
%T A068014 118,124,126,135,145,153,158,166,178,184,186,190,194,198,206,208,209,
%U A068014 216,221,224,230,232,238,250,252,254,260,266,270,278,280,295,297,298
%N A068014 Nonprimes n such that 1+Phi[n] and -1+Sigma[1,n] are prime numbers.
%F A068014 1+A000010(n) and -1+A000203(n) are primes but n is nonprime
%e A068014 n=38, Phi[38]+1=19 and Sigma[38]-1=1+2+19+39-1=59.
%t A068014 Do[s=-1+DivisorSigma[1, n]; s1=1+EulerPhi[n]; If[PrimeQ[s]&&PrimeQ[s1]&&!PrimeQ[n], 
               Print[{n, s1, s}]], {n, 1, 1000}] generates sequence and related 
               primes too;
%Y A068014 Cf. A000010, A000203, A066071-A066080.
%Y A068014 Sequence in context: A060650 A068198 A064899 this_sequence A057885 A015812 
               A080784
%Y A068014 Adjacent sequences: A068011 A068012 A068013 this_sequence A068015 A068016 
               A068017
%K A068014 nonn
%O A068014 1,1
%A A068014 Labos E. (labos(AT)ana.sote.hu), Feb 08 2002

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