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A246569 Semiprimes with strictly increasing product of digits. 4
4, 6, 9, 25, 26, 35, 38, 39, 49, 58, 69, 87, 249, 259, 278, 289, 299, 398, 478, 489, 579, 589, 679, 689, 699, 789, 799, 889, 899, 2589, 2599, 2779, 2798, 2899, 3799, 3898, 3899, 4798, 4979, 4989, 5799, 5899, 5999, 6989, 6999, 7899, 7999, 8899, 9899, 19999, 26799 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Primes of this form are at A230041.

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..169

EXAMPLE

a(6) = 35 = 5 * 7, which is semiprime. Product of its digits = 3 * 5 = 15.

a(7) = 38 = 2 * 19, which is semiprime. Product of its digits = 3 * 8 = 24.

Since 24 > 15, 35 and 38 appear in the sequence.

MATHEMATICA

A246569 = { }; t = 0; Do[s = Apply[Times, IntegerDigits[k]]; If[PrimeOmega[k] == 2 && s > t, t = s; AppendTo[A246569, k]], {k, 1, 30000}]; A246569

CROSSREFS

Cf. A001358, A230041.

Sequence in context: A046376 A229129 A272436 * A326063 A085721 A190300

Adjacent sequences:  A246566 A246567 A246568 * A246570 A246571 A246572

KEYWORD

nonn,base

AUTHOR

K. D. Bajpai, Aug 30 2014

STATUS

approved

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Last modified February 20 07:38 EST 2020. Contains 332069 sequences. (Running on oeis4.)