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A209931
Numbers n such that smallest digit of all divisors of n is 1.
5
1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 26, 27, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 55, 56, 57, 58, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 71, 72, 73, 74, 75, 76, 77, 78, 79, 81, 82, 83, 84, 85, 86, 87, 88, 89, 91, 92, 93, 94, 95, 96, 97, 98, 99, 111
OFFSET
1,2
COMMENTS
Also numbers n such that smallest digit of concatenation of all divisors of n (A037278 or A176558) is 1.
Sequence is not the same as A052382, first deviation is at a(175): A052382(175) = 214, a(175) = 215.
Sequence is not the same as A067251, first deviation is at a(91): A067251 (91) = 101, a(91) = 111.
Complement of A209932.
EXAMPLE
Number 24 is in sequence because smallest digit of all divisors of 24 (1, 2, 4, 8, 3, 6, 12, 24) is 1.
MAPLE
isA209931 := proc(n)
digsdiv := {} ;
for d in numtheory[divisors](n) do
dgs := convert(convert(d, base, 10), set) ;
digsdiv := digsdiv union dgs ;
end do:
if 0 in digsdiv then
false;
else
true ;
end if;
end proc:
A209931 := proc(n)
option remember;
if n =1 then
1;
else
for a from procname(n-1)+1 do
if isA209931(a) then
return a;
end if;
end do;
end if;
end proc:
seq(A209931(n), n=1..120) ; # R. J. Mathar, Dec 28 2023
CROSSREFS
Cf. A052382, A067251, A209929 (smallest digit of all divisors of n).
Sequence in context: A023804 A342851 A067251 * A052382 A367733 A043095
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Mar 20 2012
STATUS
approved