A246569 Semiprimes with strictly increasing product of digits.

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

Offset: 1

Author

K. D. Bajpai, Aug 30 2014

Keywords

• nonn
• base

Comments

Primes of this form are at A230041.

Examples

			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.
		

Links

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

Crossrefs

Cf. A001358, A230041.

Programs

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