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A080363 n is such that its largest prime divisor is also one of its unitary prime divisors and n is not a prime number. +0
5
6, 10, 12, 14, 15, 20, 21, 22, 24, 26, 28, 30, 33, 34, 35, 38, 39, 40, 42, 44, 45, 46, 48, 51, 52, 55, 56, 57, 58, 60, 62, 63, 65, 66, 68, 69, 70, 74, 76, 77, 78, 80, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 99, 102, 104, 105, 106, 110, 111, 112, 114, 115, 116, 117 (list; graph; listen)
OFFSET

1,1

EXAMPLE

n=20: it is not a prime, 20=2.2.5, largest prime factor is 5 and GCD[5,20/5]=1 so 5 is unitary prime divisor of 20, so 20 is here.

MATHEMATICA

ma[x_] := Part[Reverse[Flatten[FactorInteger[x]]], 2] k=0; Do[s=ma[n]; If[Equal[GCD[s, n/s], 1]&&!PrimeQ[n], Print[n]], {n, 2, 256}]

CROSSREFS

Cf. A034444, A056169, A006530.

Sequence in context: A139587 A119313 A097318 this_sequence A082300 A050703 A135711

Adjacent sequences: A080360 A080361 A080362 this_sequence A080364 A080365 A080366

KEYWORD

nonn

AUTHOR

Labos E. (labos(AT)ana.sote.hu), Feb 21 2003

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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