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Numbers n for which there is at least one x < n such that sigma(x) = sigma(n).

13

`%I #10 Dec 08 2017 16:58:14
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`%S 11,15,17,23,25,26,31,35,38,39,41,46,47,51,53,55,56,58,59,62,65,69,70,
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`%T 71,75,77,78,79,82,83,87,89,92,94,95,97,103,107,110,113,115,116,118,
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`%U 119,122,123,124,125,127,130,131,135,139,140,141,142,143,145,151,153
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`%N Numbers n for which there is at least one x < n such that sigma(x) = sigma(n).
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`%C Numbers n for which A263025(n) > 1. - _Antti Karttunen_, Dec 08 2017
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`%H Antti Karttunen, <a href="/A069822/b069822.txt">Table of n, a(n) for n = 1..10547</a>
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`%o (PARI) for(s=1,200,if(prod(i=1,s-1, sigma(i)-sigma(s))==0,print1(s,",")))
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`%o (PARI) for(n=1,16384,y=0;s=sigma(n);for(k=1,(n-1),if(sigma(k)==s,y=1;break)); if(y,i++;write("b069822.txt", i," ", n))); \\ _Antti Karttunen_, Dec 08 2017
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`%Y Cf. A263025, A296214.
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`%Y Cf. A296087 (a subsequence).
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`%K easy,nonn
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`%O 1,1
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`%A _Benoit Cloitre_, Apr 28 2002
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