This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A256935 #17 Apr 14 2015 16:45:29
%S A256935 0,3,5,7,33,11,13,35,17,19,31,311,57,37,313,317,53,511,319,59,71,73,
%T A256935 355,711,79,713,331,519,97,3311,337,113,523,3313,717,131,719,3335,137,
%U A256935 139,151,3317,531,157,353,3319,173,557,359,179,191,193,3513,197,199,311,313,3357,317,1129,331,3337,567
%N A256935 Concatenation of odd prime factors of numbers whose digits are all odd.
%C A256935 In decimal digits of a(n) there is at least one prime.
%e A256935 a(5) = 33 because the fifth odd number is 9, and the odd prime factors of 9 are 3 * 3, thus 33 is the result of the concatenation of these factors.
%t A256935 f[n_] := Block[{of = Select[Table[#1, {#2}] & @@@ FactorInteger@ n // Flatten, PrimeQ@ # && # > 2 &]}, IntegerDigits@ of // Flatten // FromDigits]; f /@ Select[Range@ 360, OddQ[Times @@ IntegerDigits[#]] &] (* _Michael De Vlieger_, Apr 13 2015 *)
%Y A256935 Cf. A119603, A256154 (Concatenation of odd prime factors of m such that the decimal digits of m only have odd prime factors).
%K A256935 base,nonn
%O A256935 1,2
%A A256935 _Giovanni Teofilatto_, Apr 13 2015