A201016 Composite numbers whose product of digits is 4.
4, 14, 22, 114, 122, 141, 212, 221, 411, 1114, 1122, 1141, 1212, 1221, 1411, 2112, 2121, 2211, 11114, 11122, 11141, 11212, 11221, 12112, 12121, 14111, 21112, 41111, 111114, 111122, 111141, 111212, 111221, 111411, 112112, 112211, 114111, 121112, 121121, 121211, 122111
Offset: 1
Examples
Number 122 is in sequence because 1*2*2=4.
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Crossrefs
Programs
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Mathematica
Select[Range[125000],CompositeQ[#]&&Times@@IntegerDigits[#]==4&] (* or *) Module[{nn=6,f,t},f=Flatten[Table[Select[FromDigits/@Permutations[PadRight[{4},d,1]],CompositeQ],{d,nn}]];t=Flatten[Table[Select[FromDigits/@Permutations[PadRight[{2,2},d,1]],CompositeQ],{d,nn}]];Join[f,t]]//Sort (* The second program is much faster than the first. *) (* Harvey P. Dale, May 15 2025 *)
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