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A072108
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Least k such that sum(i=1,k,gcd(k,i)) = n * sigma(k).
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1
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1, 40, 220, 980, 2940, 11016, 10080, 44064, 55080, 112000, 245344, 220320, 308448, 484704, 550368, 2590720, 38509344, 1349460, 3248000, 7772160, 2423520, 5464480, 51482340, 14837760, 6301152, 18135040, 19872864, 10795680, 61116768, 45323520, 120513096, 67298560, 32387040, 118295408, 49660128, 86526720, 147671040, 225392640, 105754880, 92252160, 939050112, 163215360
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OFFSET
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1,2
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COMMENTS
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a(97) <= 823547648000. - Hiroaki Yamanouchi, Jul 08 2014
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LINKS
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Hiroaki Yamanouchi, Table of n, a(n) for n = 1..96
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MATHEMATICA
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f[n_] := Block[{k = 1}, While[ Sum[ GCD[k, i], {i, 1, k}] != n*DivisorSigma[1, k], k++ ]; k]
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PROG
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(PARI) for(n=1, 5, k=1; while(abs(sum(i=1, k, gcd(k, i))-sigma(k)*n)>0, k++); print1(k, ", "))
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CROSSREFS
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Sequence in context: A235270 A181637 A111176 * A218404 A235010 A235290
Adjacent sequences: A072105 A072106 A072107 * A072109 A072110 A072111
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KEYWORD
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nonn
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AUTHOR
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Benoit Cloitre, Jun 19 2002
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EXTENSIONS
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More terms from Robert G. Wilson v, Jun 28 2002 and Jul 09 2002
Corrected and extended by Rick L. Shepherd, Jun 30 2002
a(10) from Robert G. Wilson v, Jul 09 2002
a(11)-a(42) from Robert Gerbicz, Nov 24 2010
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STATUS
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approved
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