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%I #21 Jul 14 2018 09:48:53
%S 2,3,439
%N Numbers m such that the largest prime factor of prime(m) + prime(m+1) equals m.
%C a(4), if it exists, is larger than 10^7.
%C a(4) > 5*10^14, if it exists. - _Giovanni Resta_, Jul 14 2018
%e Numbers x such that A006530(A001043(x)) = x.
%e x = 2 is a term: p(2) + p(3) = 3 + 5 = 8 with largest factor = 2 = x.
%e x = 3 is a term: p(3) + p(4) = 5 + 7 = 12 with largest factor = 3 = x.
%e x = 439 is a term: p(439) + p(440) = 3067 + 3079 = 6146 = 2*7*439 = 14x.
%t DeleteCases[#, 0] &@ MapIndexed[Boole[#1 == First@ #2] First@ #2 &, Map[FactorInteger[Total@ #][[-1, 1]] &, Partition[Prime@ Range[10^6], 2, 1]]] (* _Michael De Vlieger_, Aug 09 2017 *)
%Y Cf. A006530, A001043, A071216-A071218.
%K nonn,bref,more
%O 1,1
%A _Labos Elemer_, May 17 2002
%E Edited by _N. J. A. Sloane_, Aug 09 2017
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