Search: id:A141390
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%I A141390
%S A141390 781,5461,13021,15751,25351,29539,40501
%N A141390 Overpseudoprimes of base 5.
%C A141390 If h_5(n) is the multiplicative order of 5 modulo n, r_5(n) is the number 
               of cyclotomic cosets of 5 modulo n then, by the definition, n is 
               an overpseudoprime of base 5 if h_5(n)*r_5(n)+1=n. These numbers 
               are in A020231.In particular, if n is squarefree such that its prime 
               factorization is
%C A141390 n=p_1*...*p_k, then n is overpseudoprime of base 5 iff h_5(p_1)=...=h_5(p_k).
%C A141390 E.g. since h_5(101)=h_5(251)=h_5(401)=25, then the number 101*251*401=10165751 
               is in the sequence.
%D A141390 V. Shevelev, Overpseudoprimes, Mersenne Numbers and Wieferich Primes,
               arxiv.org /abs/0806.3412
%Y A141390 Cf. A141232 A141350 A020231 A020229.
%Y A141390 Sequence in context: A115467 A020231 A038477 this_sequence A006113 A158398 
               A003914
%Y A141390 Adjacent sequences: A141387 A141388 A141389 this_sequence A141391 A141392 
               A141393
%K A141390 nonn
%O A141390 1,1
%A A141390 Vladimir Shevelev (shevelev(AT)bgu.ac.il), Jun 29 2008

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