Search: id:A154862
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%I A154862
%S A154862 1,1,9,21,45,51,65,105,133,153,209,243,247,325,357,385,413,459,495,531,
%T A154862 675,707,729,789,805,845,891,913,951,981,1003,1067,1083,1111,1125,1203,
%U A154862 1313,1335,1347,1369,1395,1417,1557,1625,1703,1725,1935,1967,2133,2211
%N A154862 Nonprimes of the form: prime(prime(n)) - 2*n.
%e A154862 If n=1 and prime(prime(1))-2*1=prime(2)-2=3-2=1(nonprime), then 1=a(1). 
               If n=2 and prime(prime(2))-2*2=prime(3)-4=5-4=1(nonprime), then 1=a(2). 
               if n=3, then prime(prime(3))-2*3=prime(5)-6=11-6=5(prime). If n=4 
               and prime(prime(4))-2*4=prime(7)-8=17-8=9(nonprime), then 9=a(3), 
               etc.
%p A154862 for n from 1 to 100 do p := ithprime(ithprime(n))-2*n ; if not isprime(p) 
               then printf("%d,",p) ; fi; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Jan 18 2009]
%Y A154862 Cf. A006450,A141468.
%Y A154862 Sequence in context: A053476 A110680 A163205 this_sequence A020137 A020190 
               A135187
%Y A154862 Adjacent sequences: A154859 A154860 A154861 this_sequence A154863 A154864 
               A154865
%K A154862 nonn
%O A154862 1,3
%A A154862 Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jan 16 2009
%E A154862 Replaced 35 by 45. Replaced 645 by 675. R. J. Mathar (mathar(AT)strw.leidenuniv.nl), 
               Jan 18 2009

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