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A289558 Numbers with two distinct prime factors not divisible by a square larger than 4. 1
6, 10, 12, 14, 15, 20, 21, 22, 24, 26, 28, 33, 34, 35, 38, 39, 40, 44, 46, 48, 51, 52, 55, 56, 57, 58, 62, 65, 68, 69, 74, 76, 77, 80, 82, 85, 86, 87, 88, 91, 92, 93, 94, 95, 96, 104, 106, 111, 112, 115, 116, 118, 119, 122, 123, 124, 129, 133, 134, 136, 141, 142, 143, 145, 146, 148, 152 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

10 is in this sequence because A001221(10) = 2 and 10 is not divisible by a square greater than 4.

MATHEMATICA

With[{nn = 10^4, r = 2}, Take[#, 67] &@ Union@ Flatten@ Table[Function[p, {p*2^Range[Log2[nn/p]], p DeleteCases[Prime@ Range[r, PrimePi[nn/p]], q_ /; q == p]}]@ Prime@ n, {n, r, PrimePi[nn/Prime[r]]}]] (* Michael De Vlieger, Jul 10 2017 *)

PROG

(PARI) list(lim)=my(v=List()); forprime(p=5, lim\3, forprime(q=3, min(lim\p, p-2), listput(v, p*q))); for(e=1, logint(lim\3, 2), forprime(p=3, lim>>e, listput(v, p<<e))); Set(v) \\ Charles R Greathouse IV, Aug 09 2017

CROSSREFS

The union of A046388 and A100368.

Cf. A001221, A007814, A289184.

Sequence in context: A119313 A097318 A080363 * A082300 A050703 A330397

Adjacent sequences:  A289555 A289556 A289557 * A289559 A289560 A289561

KEYWORD

nonn,easy

AUTHOR

Juri-Stepan Gerasimov, Jul 08 2017

STATUS

approved

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Last modified June 24 12:30 EDT 2021. Contains 345416 sequences. (Running on oeis4.)