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26, 84, 78, 168, 118, 146, 242, 182, 208, 276, 200, 398, 396, 322, 438, 344, 390, 412, 536, 628, 432, 338, 582, 472, 558, 840, 512, 824, 640, 726, 1022, 852, 914, 628, 744, 616, 1178, 1018, 858, 1140, 856, 760, 990, 936, 1490, 1014, 1564, 1482, 1104, 1096, 1196, 1138, 1008, 1550, 1556, 1180, 1474, 1158, 1508, 858, 2020
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OFFSET
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1,1
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COMMENTS
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If a(n) > 2 for all n, then there are no odd perfect numbers. See also the conjectures in A324213.
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LINKS
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FORMULA
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PROG
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(PARI)
up_to = 25000;
isA228058(n) = if(!(n%2)||(omega(n)<2), 0, my(f=factor(n), y=0); for(i=1, #f~, if(1==(f[i, 2]%4), if((1==y)||(1!=(f[i, 1]%4)), return(0), y=1), if(f[i, 2]%2, return(0)))); (y));
A228058list(up_to) = { my(v=vector(up_to), k=0, n=0); while(k<up_to, n++; if(isA228058(n), k++; v[k] = n)); (v); };
v228058 = A228058list(up_to);
A324213(n) = { my(s=sigma(n)); sum(i=0, s, (1==gcd(n-i, n-(s-i)))); };
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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