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.

1, 16, 25, 27, 32, 49, 64, 81, 100, 108, 112, 121, 125, 128, 135, 144, 147, 160, 162, 169, 175, 189, 192, 196, 200, 216, 224, 225, 243, 245, 250, 256, 288, 289, 320, 324, 343, 361, 375, 384, 392, 400, 405, 432, 441, 448, 486, 500, 512, 529, 567, 576, 625, 640

Offset

1,2

Links

Table of n, a(n) for n=1..54.

Formula

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

Example

n=100: prime set={2,5}, 3 digits and 2 digits of prime factors, so 100 is here;
n=147: prime set={3,7}, 3 digits and 2 digits of [ -factors, so 147 is here.

Mathematica

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]]

Crossrefs

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

Sequence in context: A334392 A227651 A348320 * A339624 A111026 A124186

Adjacent sequences: A095406 A095407 A095408 * A095410 A095411 A095412

Keyword

base,nonn

Author

Labos Elemer, Jun 21 2004

Status

approved