A050696 - OEIS

%I #14 Oct 15 2019 01:40:00

%S 12,15,20,22,24,25,26,28,30,32,33,35,36,39,42,45,50,52,55,62,63,65,70,

%T 72,75,77,82,85,92,93,95,102,105,110,112,115,120,122,123,124,125,126,

%U 128,130,132,135,138,142,145,147,150,152,153,155,162,165,170,172,175

%N At least one prime factor of composite a(n) is a substring of a(n).

%H Vincenzo Librandi, <a href="/A050696/b050696.txt">Table of n, a(n) for n = 1..4720</a>

%e 26 is in the sequence because 26 = 2 * 13 and the factor 2 appears in the decimal representation. Though 13 does not appear, the 2 is enough for 26 to be in the sequence.

%e 27 is not in the sequence since 27 = 3 * 3 * 3, which does not appear in the decimal representation.

%t digs[n_] := IntegerDigits[n]; A050696 = {}; Do[le1 = Max@@Length/@(prFDigs = digs[First/@FactorInteger[n]]); dSubStrs = Flatten[Table[Partition[digs[n], i, 1], {i, le1}], 1]; If[!PrimeQ[n] && Intersection[prFDigs, dSubStrs] != {}, AppendTo[A050696, n]],{n, 2, 180}]; A050696 (* _Jayanta Basu_, May 31 2013 *)

%Y Cf. A050694, A050695.

%K nonn,base

%O 1,1

%A _Patrick De Geest_, Aug 15 1999