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A216482
a(n) is the least value of k such that k*n uses only digits 1 and 2. a(n) = -1 if no such multiple exists.
1
1, 1, 4, 3, -1, 2, 3, 14, 1358, -1, 1, 1, 17, 8, -1, 7, 13, 679, 59, -1, 1, 1, 527, 88, -1, 47, 786, 4, 418, -1, 362, 66, 34, 33, -1, 617, 3, 319, 2849, -1, 271, 291, 284, 48, -1, 2657, 26, 44, 229, -1, 22, 406, 4, 393, -1, 2, 3723, 209, 19, -1, 2, 181, 194, 33, -1, 17, 33, 1634, 3219, -1, 172, 1696, 2907, 3, -1, 1462, 1443, 1554, 28, -1, 262, 271, 134, 1443
OFFSET
1,3
LINKS
MAPLE
f:= proc(n) local d, a, i, S, R;
if n mod 5 = 0 then return -1 fi;
for d from ilog10(n)+1 do
a:= (10^d-1)/9;
S:= [seq(10^i, i=0..d-1)];
R:= select(t -> convert(t, `+`) + a mod n = 0, combinat:-powerset(S));
if R <> [] then return min(map(t -> convert(t, `+`)+a, R))/n fi
od
end proc:
map(f, [$1..100]); # Robert Israel, Dec 26 2022
CROSSREFS
KEYWORD
sign,base,look
AUTHOR
V. Raman, Sep 07 2012
STATUS
approved