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A071189
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Smallest prime factor of sum of divisors of n.
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8
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1, 3, 2, 7, 2, 2, 2, 3, 13, 2, 2, 2, 2, 2, 2, 31, 2, 3, 2, 2, 2, 2, 2, 2, 31, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 7, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 127, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 11, 2, 2, 2, 2, 2, 2, 2
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OFFSET
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1,2
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LINKS
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FORMULA
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MATHEMATICA
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Table[FactorInteger[DivisorSigma[1, n]][[1, 1]], {n, 90}] (* Harvey P. Dale, May 15 2011 *)
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PROG
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(PARI) first(n) = {my(v = vector(n, i, 2), sq = List()); for(i=1, sqrtint(n), listput(sq, i^2); listput(sq, 2*i^2)); listsort(sq); v[1]=1; for(i=2, #sq, if(sq[i]>n, break); v[sq[i]] = factor(sigma(sq[i]))[, 1]~[1]); v} \\ David A. Corneth, Jul 24 2017
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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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