A256154 Concatenation of odd prime factors of m such that the decimal digits of m only have odd prime factors.

3, 5, 7, 33, 311, 57, 37, 313, 53, 511, 319, 59, 73, 355, 711, 79, 331, 519, 97, 3311, 3337, 567, 337, 3113, 353, 571, 3717, 359, 373, 3555, 1329, 379, 3131, 579, 397, 3719, 1341, 5107, 3179, 7711, 779, 3537, 557, 1343, 3191, 5523, 577, 3193, 593, 5717, 3199, 599, 733, 3577, 1167, 739, 3251, 5151

Offset: 1

Author

Giovanni Teofilatto, Apr 14 2015

Keywords

• nonn
• base

Comments

Numbers in the sequence m cannot have even digits and 1: {3, 5, 7, 9, 33, 35, 37, 39, 53, ..., 99, 333, 335, ...}.

Subset of A256935.

Examples

			a(5) = 33 because m(5) = 9, whose odd prime factors are 3 * 3, thus 33 is the concatenation of the factors.
		

Crossrefs

Cf. A119603, A256935.

Programs

Mathematica

f[n_] := Block[{of = Select[Table[#1, {#2}] & @@@ FactorInteger@ n // Flatten, PrimeQ@ # && # > 2 &]}, IntegerDigits@ of // Flatten // FromDigits]; f /@ Select[Range@ 755, Plus @@ Pick[DigitCount@#, {1, 1, 0, 1, 0, 1, 0, 1, 0, 1}, 1] == 0 &] (* Michael De Vlieger, Apr 14 2015 *)