A050695 Composite numbers k such that none of the prime factors of k is a substring of k.

4, 6, 8, 9, 10, 14, 16, 18, 21, 27, 34, 38, 40, 44, 46, 48, 49, 51, 54, 56, 57, 58, 60, 64, 66, 68, 69, 74, 76, 78, 80, 81, 84, 86, 87, 88, 90, 91, 94, 96, 98, 99, 100, 104, 106, 108, 111, 114, 116, 117, 118, 119, 121, 129, 133, 134, 136, 140, 141, 143, 144, 146

Offset

1,1

Comments

A131929(a(n)) = 0; together with 1, complement of A131930. - Reinhard Zumkeller, Jul 30 2007

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Example

114 = 2*3*19.

Mathematica

d[n_]:=IntegerDigits[n]; t={}; Do[le1=Max@@Length/@(t1=d[First/@FactorInteger[n]]); t2=Flatten[Table[Partition[d[n], i, 1], {i, le1}], 1]; If[!PrimeQ[n]&&Intersection[t1, t2]=={}, AppendTo[t, n]], {n, 2, 146}]; t (* Jayanta Basu, May 31 2013 *)
npfsQ[n_]:=Module[{idn=IntegerDigits[n], f=FactorInteger[n][[All, 1]]}, And@@ Table[SequenceCount[idn, IntegerDigits[f[[i]]]]==0, {i, Length[ f]}]]; Select[Range[200], CompositeQ[#] && npfsQ[#]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Dec 28 2016 *)

Crossrefs

Cf. A050694, A050696, A035139, A050698.

Sequence in context: A001745 A359982 A276628 * A035139 A316227 A062115

Adjacent sequences: A050692 A050693 A050694 * A050696 A050697 A050698

Keyword

nonn,base,nice

Author

Patrick De Geest, Aug 15 1999

Status

approved