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

1,1

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.

Links

Table of n, a(n) for n=1..58.

Example

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

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 *)

Crossrefs

Cf. A119603, A256935.

Sequence in context: A256935 A095714 A137864 * A069969 A067232 A327413

Adjacent sequences: A256151 A256152 A256153 * A256155 A256156 A256157

Keyword

nonn,base

Author

Giovanni Teofilatto, Apr 14 2015

Status

approved