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A262723 Squarefree products of three primes whose prime divisors form an arithmetic progression. 0
105, 231, 627, 897, 935, 1581, 1729, 2465, 2967, 4123, 4301, 4715, 5487, 7685, 7881, 9717, 10707, 11339, 14993, 16377, 17353, 20213, 20915, 23779, 25327, 26331, 26765, 29341, 29607, 32021, 33335, 40587, 40807, 42911, 48635, 49321, 54739, 55581, 55637, 59563, 60297, 63017 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This sequence is subsequence of A046389, A088595, A187073, A203614 and A229094.

Obviously, the most repeated prime divisor for values of a(n) is 3. - Altug Alkan, Sep 30 2015

LINKS

Table of n, a(n) for n=1..42.

EXAMPLE

627 is in this sequence because 627=3*11*19, and 3, 11, 19 form an arithmetic progression (11-3 = 19-11).

MATHEMATICA

Select[Range@ 64000, And[SquareFreeQ@ #, PrimeOmega@ # == 3, Subtract @@ Differences[First /@ FactorInteger@ #] == 0] &] (* Michael De Vlieger, Sep 30 2015 *)

PROG

(PARI) for(i=2, 10^5, if(issquarefree(i)&&omega(i)==3, f=factor(i); if(f[1, 1]+f[3, 1]==2*f[2, 1], print1(i, ", "))))

CROSSREFS

Cf. A046389, A088595, A187073, A203614, A229094.

Sequence in context: A176878 A088595 A229094 * A250757 A146257 A075764

Adjacent sequences:  A262720 A262721 A262722 * A262724 A262725 A262726

KEYWORD

nonn

AUTHOR

Antonio Roldán, Sep 28 2015

STATUS

approved

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Last modified April 27 06:52 EDT 2017. Contains 285508 sequences.