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A059113
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Numbers that are the sum of the divisors of two distinct coprime squares.
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1
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31, 187131, 347529, 658749, 2106853, 3969147, 4657471, 4980801, 6540807, 10185273, 20421219, 25690413, 42827421, 44136183, 51598911, 73854183, 202765017, 299457613, 307464339, 308953281, 314858271, 504081669, 516979281, 600877641, 613602549
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OFFSET
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1,1
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LINKS
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EXAMPLE
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31 = sigma(4^2) = sigma(5^2); 187131 = sigma(326^2) = sigma(407^2); etc.
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PROG
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(PARI) m=10^5; m2=m^2; s=vector(m); ss=vector(m); v=vector(49); for(j=1, m, s[j]=sigma(j^2)); ss=vecsort(s); c=0; for(j=2, m, if(s[j]>m2, next); if(s[j]>=ss[j], for(k=j, m-1, if(s[j]==ss[k], if(s[j]<>ss[k+1], next(2)); k=m-1)), forstep(k=j-1, 2, -1, if(s[j]==ss[k], if(s[j]<>ss[k-1], next(2)); k=2))); for(k=j+1, m, if(s[j]==s[k], if(gcd(j, k)==1, c++; v[c]=s[j])))); v=vecsort(v); n=0; for(j=2, 49, if(v[j-1]<>v[j], n++; print(n " " v[j]))) /* Donovan Johnson, Apr 20 2013 */
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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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