A043432 Numbers having four 2's in base 8.

1170, 5266, 8338, 8850, 9234, 9298, 9346, 9354, 9360, 9361, 9363, 9364, 9365, 9366, 9367, 9370, 9378, 9386, 9394, 9402, 9426, 9490, 9554, 9618, 9682, 9874, 10386, 10898, 11410, 11922, 13458, 17554, 21650, 25746, 29842

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• base

Links

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

Crossrefs

Cf. A007094.

Programs

Maple

F:= proc(d) local r, L,M,S, Res; # to get all terms < 8^d
   Res:= NULL;
   for S in combinat:-choose(d,d-4) do
     L:= Vector(d,2);
     for r from 0 to 7^(d-4)-1 do
       M:= subs(2=7,convert(r+7^(d-4),base,7)[1..d-4]);
       L[S]:= Vector(M);
       Res:= Res, add(8^(i-1)*L[i],i=1..d);
     od
   od;
   sort([Res]);
end proc:
F(6); # Robert Israel, Mar 20 2018

Mathematica

Select[Range[0, 30000], DigitCount[#, 8, 2]==4 &] (* Vincenzo Librandi, Mar 21 2018 *)

PARI

isok(n) = #select(x->(x==2), digits(n, 8)) == 4; \\ Michel Marcus, Mar 21 2018