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A083538
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a(n)=A060781[n]/A060780[n]=A083539[n]/A060780[n]^2; quotient when LCM of sigma[n+1] and sigma[n] is divided by GCD of sigma[n+1] and sigma[n].
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15
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3, 12, 28, 42, 2, 6, 120, 195, 234, 6, 21, 2, 84, 1, 744, 558, 78, 780, 210, 336, 72, 6, 10, 1860, 1302, 420, 35, 420, 60, 36, 2016, 336, 72, 72, 4368, 3458, 570, 210, 1260, 105, 112, 264, 231, 182, 156, 6, 372, 7068, 589, 744, 1764, 1323, 180, 15, 15, 6, 72, 6, 70
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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FORMULA
| a(n) = LCM[phi[n+1], phi[n]]/GCD[phi[n+1], phi[n]] = (phi[n+1].phi[n])/GCD[phi[n+1], phi[n]]^2 = A083542(n)/A060780(n)^2.
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EXAMPLE
| n=10: sigma[10]=18, sigma[11]=12, lcm[18, 12]=36, gcd[18, 12]=6, a(10)=36/6=6.
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MATHEMATICA
| f[x_] := DivisorSigma[1, x] t=Table[LCM[f[w+1], f[w]]/GCD[f[w+1], f[w]], {w, 1, 128}]
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CROSSREFS
| Cf. A000010, A066813, A058515.
Cf. A000203, A060781, A060780, A083539.
Sequence in context: A133647 A009222 A083543 * A060781 A083539 A066643
Adjacent sequences: A083535 A083536 A083537 * A083539 A083540 A083541
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), May 21 2003
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Apr 29 2007
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