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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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0
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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MATHEMATICA
| f[n_] := Block[{k = 1}, While[ Sum[ GCD[k, i], {i, 1, k}] != n*DivisorSigma[1, k], k++ ]; k]
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PROG
| (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
| Sequence in context: A077818 A181637 A111176 * A074360 A068790 A073962
Adjacent sequences: A072105 A072106 A072107 * A072109 A072110 A072111
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KEYWORD
| more,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Jun 19 2002
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EXTENSIONS
| More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 28 2002 and Jul 09 2002
Corrected and extended by Rick L. Shepherd (rshepherd2(AT)hotmail.com), Jun 30 2002
a(10) from Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 09 2002
a(11)-a(42) from Robert Gerbicz (robert.gerbicz(AT)gmail.com), Nov 24 2010
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