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A043452 Numbers n such that number of 7's in base 8 is 4. 1
4095, 8191, 12287, 16383, 20479, 24575, 28671, 29183, 29695, 30207, 30719, 31231, 31743, 32255, 32319, 32383, 32447, 32511, 32575, 32639, 32703, 32711, 32719, 32727, 32735, 32743, 32751, 32759, 32760, 32761, 32762, 32763, 32764, 32765, 32766, 36863, 40959, 45055 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MAPLE

G:= proc(x, c, d) local L, m1, m2;

     L:= convert(x, base, 7);

     m2:= nops(c);

     m1:= min(nops(L), m2);

     8^d-1 + add((L[i]-7)*8^(c[i]-1), i=1..m1) - 7*add(8^(c[i]-1), i = m1+1..m2)

end proc:

sort([seq(seq(G(x, c, 6), x = 0 .. 7^2-1), c=combinat:-choose(6, 2))]); # Robert Israel, Sep 24 2017

MATHEMATICA

Select[Range[0, 10^5], DigitCount[#, 8, 7]==4 &] (* Vincenzo Librandi, Sep 25 2017 *)

PROG

(PARI) isok(n) = #select(x->(x==7), digits(n, 8)) == 4; \\ Michel Marcus, Sep 25 2017

CROSSREFS

Sequence in context: A145591 A103289 A038463 * A261593 A290869 A075952

Adjacent sequences:  A043449 A043450 A043451 * A043453 A043454 A043455

KEYWORD

nonn,base

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified December 13 19:41 EST 2018. Contains 318087 sequences. (Running on oeis4.)