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Search: id:A080366
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| A080366 |
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n is such that neither of its least nor the largest prime divisors are unitary prime divisors of n. |
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+0
1
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| 4, 8, 9, 16, 25, 27, 32, 36, 49, 64, 72, 81, 100, 108, 121, 125, 128, 144, 169, 196, 200, 216, 225, 243, 256, 288, 289, 300, 324, 343, 361, 392, 400, 432, 441, 484, 500, 512, 529, 576, 588, 600, 625, 648, 675, 676, 729, 784, 800, 841, 864, 900, 961, 968, 972
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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n=300: it is not a prime, 300=2.2.3.5.5; extremal prime factors are 2 and 5; GCD[2,90/2]=GCD[5,90/5]>1 so 2 and 5 are not unitary-prime-divisor of 300, thus 300 is here.
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MATHEMATICA
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ma[x_] := Part[Reverse[Flatten[FactorInteger[x]]], 2] mi[x_] := Part[Flatten[FactorInteger[x]], 1] k=0; Do[s=mi[n]; s1=ma[n]; If[ !Equal[GCD[s, n/s], 1]&&!Equal[GCD[s1, n/s1], 1]&&!PrimeQ[n], Print[n]], {n, 2, 1000}]
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CROSSREFS
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Cf. A034444, A056169, A020639, A006530, A080363, A080364, A080365.
Sequence in context: A100657 A127398 A109422 this_sequence A001694 A001597 A072777
Adjacent sequences: A080363 A080364 A080365 this_sequence A080367 A080368 A080369
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Feb 21 2003
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