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Numbers having three 0's in base 8.
1

%I #14 Apr 24 2021 17:40:13

%S 512,1024,1536,2048,2560,3072,3584,4097,4098,4099,4100,4101,4102,4103,

%T 4104,4112,4120,4128,4136,4144,4152,4160,4224,4288,4352,4416,4480,

%U 4544,4608,5120,5632,6144,6656,7168,7680,8193,8194

%N Numbers having three 0's in base 8.

%H Robert Israel, <a href="/A043423/b043423.txt">Table of n, a(n) for n = 1..10000</a>

%p g:= proc(x) local j; seq(8*x+j,j=1..7) end proc:

%p h:= x -> 8*x:

%p B[1,0]:= {$1..7}:

%p for d from 2 to 5 do

%p B[d,0]:= map(g, B[d-1,0]);

%p for i from 1 to min(d-2,3) do

%p B[d,i]:= map(g, B[d-1,i]) union map(h, B[d-1,i-1])

%p od;

%p if d <= 4 then B[d,d-1]:= map(h, B[d-1,d-2]) fi;

%p od:

%p sort(convert(B[4,3] union B[5,3], list)); # _Robert Israel_, Jan 15 2019

%t Select[Range[10000],DigitCount[#,8,0]==3&] (* _Harvey P. Dale_, Nov 25 2018 *)

%Y Cf. A007094.

%K nonn,base

%O 1,1

%A _Clark Kimberling_