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A325204 Numbers k such that k*(k+1)*(k+2) has exactly 4 distinct prime factors. 3
5, 9, 10, 11, 12, 14, 15, 17, 18, 22, 23, 24, 25, 26, 27, 30, 31, 32, 36, 46, 47, 48, 52, 62, 71, 72, 79, 80, 81, 96, 106, 107, 126, 127, 162, 191, 192, 241, 242, 256, 382, 431, 486, 512, 576, 862, 1151, 1152, 2186, 2591, 2592, 2916, 4372, 8191, 8746, 131071, 131072, 139967, 472391, 524287, 786431, 995326, 995327 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Contains 2^p-1 for p in A107360 except 3.

Contains all members of A325255 except 2 and 4.

Contains k-1 for k in A027856 except 4.

Contains k-2 for k in A327240 except 6 and 8. - Ray Chandler, Sep 14 2019

LINKS

Ray Chandler, Table of n, a(n) for n = 1..178 (terms < 10^1000, first 114 terms from Robert Israel)

Ray Chandler, Mathematica code used to compute b-file.

Math StackExchange, Three consecutive numbers with exactly different four prime factors

EXAMPLE

a(3)=10 is in the sequence because 10*11*12 has four distinct prime factors: 2, 3, 5, 11.

MAPLE

select(t -> nops(numtheory:-factorset(t) union numtheory:-factorset(t+1) union numtheory:-factorset(t+2))=4, [$1..10^6]);

PROG

(PARI) select(k->4==omega(k*(k+1)*(k+2)), [1..10000]) \\ Andrew Howroyd, Sep 05 2019

CROSSREFS

Cf. A027856, A107360, A325255, A327240.

Sequence in context: A314583 A205712 A093711 * A163670 A187713 A101082

Adjacent sequences:  A325201 A325202 A325203 * A325205 A325206 A325207

KEYWORD

nonn

AUTHOR

J. M. Bergot and Robert Israel, Sep 05 2019

STATUS

approved

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Last modified November 19 16:37 EST 2019. Contains 329323 sequences. (Running on oeis4.)