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Search: id:A072109
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| A072109 |
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Numbers n such that sum(i=1,n,gcd(n,i)) divides sum(i=1,n,lcm(n,i)). |
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+0
2
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| 1, 4, 36, 125, 469, 536, 882, 1156, 8532, 8775, 25012, 32000, 34749, 36324, 37179, 61952, 147456, 405224, 451584, 644304, 954084, 1185921
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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n such that A018804(n) divides A051193(n)
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MAPLE
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with(numtheory): for n from 1 to 10^6 do a := divisors(n): s1 := add(a[m]*phi(a[m]), m=1..nops(a)): s2 := add(phi(a[m])/a[m], m=1..nops(a)): if type((s1+1)/(2*s2), integer) then printf(`%d, `, n); fi: od:
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MATHEMATICA
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f[n_] := (k = n; While[ !IntegerQ[ Sum[ LCM[k, i], {i, 1, k}] / Sum[ GCD[k, i], {i, 1, k}]], k++ ]; k); j = 1; Do[ m = f[j]; Print[m]; j = m + 1, {n, 1, 9}]
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PROGRAM
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(PARI) for(n=1, 1156, if(sum(i=1, n, lcm(n, i))%sum(i=1, n, gcd(n, i))==0, print1(n, ", ")))
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CROSSREFS
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Sequence in context: A016826 A038688 A076830 this_sequence A045490 A060783 A125756
Adjacent sequences: A072106 A072107 A072108 this_sequence A072110 A072111 A072112
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KEYWORD
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more,nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Jun 19 2002
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EXTENSIONS
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Edited by Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 22 2002
More terms from Vladeta Jovovic (vladeta(AT)Eunet.yu), Jun 22 2002
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