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
KEYWORD
nonn,base
AUTHOR
STATUS
approved