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Search: id:A080365
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| A080365 |
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n is such that both of its least and largest prime divisors are also its unitary prime divisors and n is not a prime number. |
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2
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| 6, 10, 14, 15, 21, 22, 26, 30, 33, 34, 35, 38, 39, 42, 46, 51, 55, 57, 58, 62, 65, 66, 69, 70, 74, 77, 78, 82, 85, 86, 87, 90, 91, 93, 94, 95, 102, 105, 106, 110, 111, 114, 115, 118, 119, 122, 123, 126, 129, 130, 133, 134, 138, 141, 142, 143, 145, 146, 154, 155, 158
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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n=90: it is not a prime, 90=2.3.3.5; extremal prime factors are 2 and 5; GCD[2,90/2]=GCD[5,90/5]=1 so 2 and 5 are unitary-prime-divisor of 90, thus 90 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, 256}]
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CROSSREFS
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Cf. A034444, A056169, A020639, A006530, A080363, A080364.
Sequence in context: A119847 A119899 A130092 this_sequence A000469 A120944 A052053
Adjacent sequences: A080362 A080363 A080364 this_sequence A080366 A080367 A080368
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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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