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A095409 Numbers n such that total number of decimal digits of all distinct prime factors of n is smaller than number of digits of n. 2

%I #5 Oct 15 2013 22:32:25

%S 1,16,25,27,32,49,64,81,100,108,112,121,125,128,135,144,147,160,162,

%T 169,175,189,192,196,200,216,224,225,243,245,250,256,288,289,320,324,

%U 343,361,375,384,392,400,405,432,441,448,486,500,512,529,567,576,625,640

%N Numbers n such that total number of decimal digits of all distinct prime factors of n is smaller than number of digits of n.

%F Solutions to A095407[x] < A055642[x].

%e n=100: prime set={2,5}, 3 digits and 2 digits of prime factors, so 100 is here;

%e n=147: prime set={3,7}, 3 digits and 2 digits of [ -factors, so 147 is here.

%t ffi[x_] :=Flatten[FactorInteger[x]] lf[x_] :=Length[FactorInteger[x]] ba[x_] :=Table[Part[ffi[x], 2*j-1], {j, 1, lf[x]}] tdp[x_] :=Flatten[Table[IntegerDigits[Part[ba[x], j]], {j, 1, lf[x]}], 1] pl[x_] :=Length[tdp[x]] nl[x_] :=Length[IntegerDigits[x]] t1=Table[nl[w], {w, 1, 1000}];t2=Table[pl[w], {w, 1, 1000}];t2-t1 Flatten[Position[t2-t1, -1]]

%Y Cf. A055642, A095407, A095408, A095410, A095411.

%K base,nonn

%O 1,2

%A _Labos Elemer_, Jun 21 2004

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Last modified May 30 15:08 EDT 2024. Contains 372968 sequences. (Running on oeis4.)