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A015791
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a(n) is the smallest integer k such that phi(k) + n | sigma(k + n).
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2
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1, 2, 4, 7, 6, 1, 9, 3, 2, 65, 4, 50, 15, 156, 8, 60, 6, 80, 6, 15, 10, 126, 16, 49, 14, 33, 12, 1, 26, 60, 72, 51, 24, 103, 74, 10, 26, 69, 54, 97, 4, 200, 33, 9, 58, 105, 34, 89, 30, 144, 66, 175, 8, 83, 6, 123, 82, 15, 120, 1682, 42, 135, 58, 73, 30, 71, 10
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OFFSET
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0,2
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LINKS
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MATHEMATICA
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Array[Block[{k = 1}, While[Mod[DivisorSigma[1, k + #], EulerPhi[k] + #] != 0, k++]; k] &, 67, 0] (* Michael De Vlieger, Dec 10 2018 *)
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PROG
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(PARI) a(n) = {my(k=1); while(frac(sigma(k+n)/(eulerphi(k)+n)), k++); k; } \\ Michel Marcus, Dec 11 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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