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A307636
Numbers k with property that no two divisors of k share a common digit.
1
1, 2, 3, 4, 5, 6, 7, 8, 9, 23, 27, 29, 37, 43, 47, 49, 53, 59, 67, 73, 79, 83, 86, 87, 89, 97, 223, 227, 229, 233, 239, 257, 263, 267, 269, 277, 283, 293, 307, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 409, 433, 439, 443, 449, 457, 463, 467, 479, 487, 499, 503
OFFSET
1,2
LINKS
Giorgos Kalogeropoulos, Hostile Divisor Numbers, Code Golf, May 2019.
EXAMPLE
9566 is such a number because its divisors are 1, 2, 4783 and 9566, and no two of them share the same digit.
MAPLE
filter:= proc(n) local D, i, j;
D:= map(t -> convert(convert(t, base, 10), set), convert(numtheory:-divisors(n), list));
for i from 2 to nops(D) do
for j from 1 to i-1 do
if D[i] intersect D[j] <> {} then return false fi
od od;
true
end proc:
select(filter, [$1..1000]); # Robert Israel, Jul 07 2019
MATHEMATICA
Select[Range@1000, !Or@@IntersectingQ@@@Subsets[IntegerDigits@Divisors[#], {2}]&]
PROG
(PARI) isok(k) = {my(d = divisors(k), dd = apply(x->Set(digits(x)), d)); for (i=1, #dd, for (j=i+1, #dd, if (#setintersect(dd[i], dd[j]), return (0)); ); ); return (1); } \\ Michel Marcus, Jul 07 2019
(Python)
from itertools import count, combinations, islice
from sympy import divisors
def A307636gen(): return filter(lambda n:all(len(set(s[0])&set(s[1])) == 0 for s in combinations((str(d) for d in divisors(n, generator=True)), 2)), count(1))
A307636_list = list(islice(A307636gen(), 20)) # Chai Wah Wu, Dec 08 2021
CROSSREFS
A038603 is a subsequence.
Sequence in context: A272814 A322516 A132080 * A373722 A048386 A302503
KEYWORD
nonn,base
AUTHOR
STATUS
approved