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Search: id:A037197
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| A037197 |
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Number of divisors of sigma(n) = number of divisors of n. |
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4
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| 1, 2, 8, 12, 32, 52, 75, 84, 90, 98, 128, 150, 156, 338, 360, 392, 525, 528, 560, 600, 722, 867, 912, 972, 1050, 1352, 1452, 1456, 1525, 1734, 1922, 2064, 2160, 2340, 2400, 2888, 2890, 3050, 3120, 3216, 3698, 3744, 3872, 4080, 4144, 4200, 4500, 4575
(list; graph; listen)
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OFFSET
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0,2
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FORMULA
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Solutions to A000005(x)=A062068(x)=A000005[A000203(x)]
Conjecture: for n > 10^6, a(n) < n^2. - Benoit Cloitre, Aug 24, 2002
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EXAMPLE
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x = 75: D[75] = {1, 3, 5, 15, 25, 75}, D[sigma(75)] = D[124] = {1, 2, 4, 31, 62, 124}, both x and sigma[x] have 6 divisors, so 75 is here.
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MATHEMATICA
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Do[s=DivisorSigma[0, DivisorSigma[1, n]]; s0=DivisorSigma[0, n]; If[Greater[s0, s], Print[n]], {n, 1, 1000}]
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CROSSREFS
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Cf. A000005, A000203, A062068, A073802-A073804.
Sequence in context: A048074 A126775 A069185 this_sequence A125712 A062290 A078541
Adjacent sequences: A037194 A037195 A037196 this_sequence A037198 A037199 A037200
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KEYWORD
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easy,nonn
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AUTHOR
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Naohiro Nomoto ( 6284968128(AT)geocities.co.jp)
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